Unit 6 Cardiac Catheterization and Angiography

UNIT 6 CARDIAC CATHETERIZATION AND ANGIOGRAPHY

Structure 6.0 Objectives 6.1 Introduction 6.2 Ventriculography 6.3 Aortography 6.4 Pulmonary Angiography 6.5 Intracardiac Pressures 6.6 Shunts 6.7 Coronary Angiography 6.8 Stenotic and Regurgitant Lesions 6.9 Percutaneous Interventions 6.10 Let Us Sum Up 6.11 Answers to Check Your Progress

6.0 OBJECTIVES

After reading this unit, you will be able to:

• enumerate the various types angiography such as coronary angiography, pulmonary angiography, ventriculography and aortography;

• enlist the indicators, contraindication of various types of angiography; and

• give a description of techniques of percutaneous intervention techniques.

6.1 INTRODUCTION

In the previous block we have discussed about the echocardiography. Here, we shall discuss about the special investigation techniques such as cardiac catheterization and angiography. The purpose of this unit is to give you an overview and insight into the world of Cardiac Catheterization and Angiography. This write up will enable you to assess the magnitude and importance of shunt lesions as well as stenotic and regurgitant lesions. Above all, it will open up a Pandora’s Box of the ever expanding horizon of interventional cardiology including coronary interventions and valvuloplasties.

1 6.2 VENTRICULOGRAPHY

Cardiac ventriculography is a diagnostic test, i.e., used to define the anatomy and function of the ventricles (left and right) and related structures. Left Ventriculography Left ventriculography is helpful in the assessment of the following parameters: 1) Segmental and global LV function 2) Mitral valve regurgitation 3) Ventricular septal defect–their presence, location and severity 4) Hypertrophic cardiomyopathy Right Ventriculography Rarely performed in adults. Useful in assessment of: 1) Segmental and global RV function 2) Assessment of RV in Congenital heart disease. Choice of Catheters for Ventriculography 1) Pigtail Catheter: This catheter developed by Judkins has end hole and side holes. The end hole permits insertion of the catheter over a J-tipped guide wire so that it can be safely advanced into the ventricle. The loop keeps the end hole away from direct contact with the endocardium. The multiple side holes permit simultaneous exit routes for the contrast and help to stabilize the catheter and prevent recoil. 2) Sones Catheter 3) NIH and Eppendorf Catheters 4) Lehman Catheter Injection Site This is best achieved by injecting directly into the ventricular chamber. Midcavitary position of the catheter ensures that there is no ventricular ectopy; sufficient contrast is delivered to chamber and apex, valve function is not interfered with and there is no endocardial staining. Injection Rate and Volume A pressure injector or flow injector can be used to deliver contrast material into the ventricle. Most laboratories follow a pressure cut-off of 1000 psi. For the pigtail and most of the other catheters, an injection rate of 10 to16 ml/sec and a volume of 30 to 55 ml is desirable. Care should be taken to avoid air embolism. Filming Projection and Technique Biplane ventriculography is preferred over single plane ventriculography because it gives more information without additional risk to the patient. Whether it is biplane or single plane ventriculography, one should use a view that gives maximum information of the area of interest with minimal overlapping of adjacent structures. For biplane ventriculography, the preferred view is 30° right anterior oblique (RAO) and 60° left anterior oblique (LAO). For single plane it is 30° RAO and 45° to 60° LAO views. For routine ventriculography, cineangiography at 30 frames/sec using a 9 inch field of view is recommended.

2 Analysis of the Ventriculogram The Ventriculogram should be assessed for: — global and regional systolic ventricular function. — degree of valvular regurgitation. — any other specific area of interest. Complications of Ventriculography Complications of Injection 1) Arrhythmias 2) Endocardial staining 3) Fascicular block 4) Embolism–Air or thrombus Alternatives to Contrast Ventriculography 1) Echocardiography 2) Magnetic Resonance Imaging 3) Electromechanical mapping

6.3 AORTOGRAPHY

Visualization of the aorta and its branches is possible by several modalities today. Apart from angiography, aorta can also be visualized non-invasively by echocardiography, CT scan imaging and by MR Angiography imaging techniques. For aortography, radiographic imaging techniques are used. These techniques have evolved over the years and have reached a high level of sophistication. Further Digital Subtraction Angiography (DSA) has been added to the armamentarium to enhance the quality of images and information obtained from this procedure. Catheters and Guide Wires The commonly used guide wires vary in diameter from 0.012 to 0.052; with 0.035 or 0.038 being the most commonly used sizes. The standard length varies from 100 to 180 cm. The exchange length catheters vary from 260 to 300 cm and help to keep the wire tip in a particular position during catheter exchange. Catheter tip configurations include straight, angled or J-tip. Catheters sizes most commonly used are 5F, 6F or 7F. They may be only end-hole, end hole and side hole or only side-hole systems. Thoracic aorta visualization requires 100-120 cm length while abdominal aorta requires 60-80 cm length. Several catheters have been used for aortography, namely, straight catheter, pigtail or tennis racquet catheter, simple curved catheter and complex reverse curve catheter. The pigtail catheter is by far the most commonly used catheter. Contrast Agents Low osmolar contrast agents are preferred because of they deliver less osmotic load, cause less local pain, less intravascular volume augmentation and less allergic reactions. CO2 and Gadolinium are emerging as useful alternative contrast agents.

3 Vascular Access Femoral and brachial arteries are still the commonest routes of access for aortography. Thoracic Aorta A sound knowledge of the anatomy of the aorta is essential prior to performing aortography. The common disorders of thoracic aorta which can be diagnosed by aortography are: 1) Coarctation of aorta 2) Patent ductus arteriosus 3) Aortic aneurysms 4) Aortic dissection 5) Vasculitides–inflammatory diseases of aorta

6) Connective tissue disorders Thoracic Aortography Aortic arch angiography has been used to assess aortic valve or aortic root disease. Thoracic aortography is helpful for assessment of aneurysms, dissection, vascular rings, coarctation, patent ductus arteriosus as well as assessment of stenoses of origin of great vessels. It is also helpful in assessment of aorta after blunt or penetrating injuries to chest wall. Abdominal Aortography The abdominal aorta starts at the level of diaphragm (T12). Here too, prior to performing an abdominal aortogram, a sound knowledge of its anatomy is absolutely essential. Abdominal aortography is performed by femoral approach using a 5F, 6F or 7F pigtail or tennis racquet catheter. If femoral access is not possible, translumbar, axillary, brachial or radial approaches may be helpful. The catheter tip is kept at T12 or L1 level. About 30 to 60 ml of contrast is injected at a rate of 15 to 30ml/sec. At least two views of aorta-AP and lateral are often enough to provide necessary information. Abdominal aortography is useful in assessment of Abdominal Aortic Aneurysms (AAA), Atherosclerotic occlusive disease (ASO), Thrombotic occlusions, Leriche syndrome, Congenital coarctation syndromes, Renal artery involvement, Middle aortic syndrome (Abdominal aortic coarctation), and stenosis/occlusion of the various branches arising from abdominal aorta. Treatment options for the various disorders include: 1) Percutaneous transluminal Angioplasty 2) Surgical Bypass grafting 3) Endovascular stenting for Abdominal aortic aneurysms

6.4 PULMONARY ANGIOGRAPHY

Pulmonary angiography is the angiographic opacification of the main and pulmonary artery and its branches. By radiographic techniques, it is possible to picturize up to seventh order pulmonary arteries. Newer imaging modalities like CT and MR angiography are fast emerging as superior

4 alternatives to angiography but there is a need to hold on to this modality in view of its therapeutic potential.

Indications

1) Pulmonary embolism — In view of the limited ability of CT and MRA to detect sub segmental emboli, pulmonary angiography with direct super selective injections may offer better resolution.

2) Vasculitis

3) Congenital abnormalities of pulmonary arteries

4) Acquired abnormalities of pulmonary arteries

5) Tumour encasement

6) Pulmonary vascular malformation

Technical Requirements

Digital subtraction pulmonary angiography with selective pulmonary arterial injections is vastly superior to conventional cut film angiography in all aspects except in resolution.

Contraindications

Absolute: None

Relative

1) Individuals with LBBB may develop complete heart block due to catheter trauma

2) Pulmonary hypertension

3) Anaphylactoid reaction to intravenous contrast

4) Patients on amiodarone

Venous Access

The femoral vein is the preferred venous access site. However, if there is proximal thrombus, then the alternative venous access sites are right or left internal jugular vein, right or left basilic vein in the antecubital fossa.

Pulmonary Catheterization

A 6F or 7F pulmonary catheter is placed over the wire in the pulmonary artery. A sidearm sheath can be left in place if it is intended to follow the study with thrombolytic therapy.

The commonly used catheters for pulmonary angiography are:

1) Straight body pigtail catheter

2) Angled pigtail catheter

5 3) Balloon catheter

Haemodynamic Assessment

This should be done prior to contrast injection.

1) All right heart and pulmonary artery pressures.

2) Damping of pressure in MPA may indicate massive embolism.

3) Pulmonary artery wedge pressure can be measured by using a balloon floatation catheter.

Contrast Media

It is recognized that contrast media can itself generate thrombus and cause embolism. A low osmolar iodinated contrast medium is preferable. For right and left pulmonary arteries, 40 to 50 ml of contrast at 20 to 25 ml/sec is required. When digital subtraction angiography is used, 25 ml of contrast is often enough. Balloon occlusion angiography of segmental vessels requires 5 to 10 ml of contrast.

Filming

Two views of each lung are performed — frontal view and 45° right (for right lung) and left (for left lung) posterior oblique views. For most indications, filming at 6 images per second is sufficient.

Anatomy and Physiology

The anatomy and physiology of the pulmonary arteries has already been dealt with in other sections and will not be repeated here.

Angiographic Findings and Interpretation Pulmonary angiography is useful in the following clinical scenarios: 1) Pulmonary artery stenosis 2) Pulmonary arteriovenous communications 3) Diffuse or focal attenuation of pulmonary vessels 4) Intraluminal abnormalities: a) Acute pulmonary thromboembolism b) Chronic pulmonary thromboembolism c) Pulmonary vascular neoplasms d) Pulmonary artery aneurysms 5) Miscellaneous: a) Inflammation—infectious and non-infectious inflammatory diseases. b) Hemorrhage—hemoptysis c) Foreign bodies

6 6.5 INTRACARDIAC PRESSURES

A pressure wave is the cyclical force generated by cardiac muscle contraction. Its amplitude and duration are influenced by various mechanical and physiological parameters. The pressure waveform of a cardiac chamber is influenced by the following factors: 1) Force of contraction of the contracting chamber 2) Its surrounding structures 3) Contiguous chambers of the heart 4) The pericardium 5) The lungs 6) The vasculature 7) The heart rate 8) The respiratory cycle For the assessment of intracardiac pressures, two systems are currently in use: 1) Fluid filled systems 2) Micromanometer catheters Atrial Pressure The RA pressure wave form has three positive deflections — “a”, “c”, and “v” waves. The “a” wave is due to atrial systole and follows the P-wave on surface ECG. The “x” descent follows the “a” wave and represents atrial relaxation and downward pulling of the tricuspid annulus by RV contraction. The “x” descent is interrupted by the “c” wave, which is a small positive deflection caused by protrusion of the closed tricuspid valve into the RA. The pressure in the RA rises after the “x” descent due to passive atrial filling. The atrial pressure then peaks as the “v” which represents ventricular systole. The LA pressure waveform is similar to that of the RA although normal LA pressure is higher representing the high pressure system of the left side of the heart. In LA pressures, unlike RA pressures, the “v” wave is generally higher than the “a” wave. Normal pressure waveforms

Normal pressure waveforms Pressures Average (mmHg) Range (mmHg) Right atrium A wave 6 2-7 V wave 5 2-7 Mean 3 1-5 Right ventricle Peak systolic 25 15-30

7 End-diastolic 4 1-7 Pulmonary artery Peak systolic 25 15-30 End-diastolic 9 4-12 Mean 15 9-19 Pulm .cap.wedge Mean 9 4-12 Left atrium A wave 10 4-16 V wave 12 6-21 Mean 8 2-12 Left ventricle Peak systolic 130 90-140 End diastolic 8 5-12 Central aorta Peak systolic 130 90-140 End diastolic 70 60-90 Mean 85 70-105 Vas. Resistances Mean (dyne-sec.cm-5) Range (dyne-sec.cm-5) Syst.vas.resist 1100 700-1600 Total pulm.resist 200 100-300 Pulm.vas.resist 70 20-130

Fig. 6.1: Normal pressure waveform

8 Pulmonary Capillary Wedge Pressure The PCW waveform is similar to LA pressure waveform except that it is damped and delayed due to transmission through the lungs. The “c” waves may not be seen. Normally the PA diastolic pressure is similar to the mean PCW pressure as the pulmonary circulation has a low resistance. Ventricular Pressure RV and LV waveforms are similar in morphology but different in magnitude. The duration of systole and isovolumic contraction and relaxation are longer and the ejection period shorter in the LV than in the RV. End diastolic pressure in generally measured at the “C” point which is the rise in ventricular pressure at the onset of isovolumic contraction. Great Vessel Pressures The contour of the central aortic pressure and PA pressure tracing consists of a systolic wave, the incisura (indicative of closure of the semilunar valves) and a gradual decline in pressure until the following systole. The pulse pressure reflects the volume and compliance of the arterial system. The mean aortic pressure more accurately reflects the peripheral resistance. Check Your Progress 1 1) What is the range of the left ventricular end diastolic pressure? ...... 2) What is the normal range of pressure in the pulmonary artery? ......

6.6 SHUNTS

Detection, localization and quantification of intracardiac shunts are one of the most important exercises in cardiac catheterization. In most cases a preliminary clinical evaluation will give us knowledge of the possible intracardiac shunt. The pointers to the presence of a shunt are: 1) Unexplained arterial desaturation (arterial saturation < 95 per cent) suggestive of a right to left shunt and representing alveolar hypoventilation. 2) Unexpectedly high pulmonary artery saturation > 80 per cent-suggestive of a left to right shunt. 3) When data at catheterization does not confirm a particular lesion. Detection of left to right intracardiac shunts—Measurement of blood oxygen saturation and content in the right heart (oximetry run) Oximetry run is a basic technique for detecting and quantifying intracardiac shunts. The oxygen content or per cent saturation is measured in blood samples drawn sequentially from PA, RV, RA, SVC and IVC. A significant step-up is defined as an increase in the blood oxygen content or saturation that exceeds the normal variability that might be observed if multiple

9 samples were drawn from that cardiac chamber. Oxygen content can be calculated from the knowledge of percentage saturation, the patient’s hemoglobin concentration and an assumed constant relationship for oxygen carrying capacity of hemoglobin (1.36mL O2/g hemoglobin).

Sites for Oximetry Run Draw 2ml blood from the following recommended sites: Left and/or right pulmonary artery Main pulmonary artery Right ventricular outflow tract Right ventricle — mid Right ventricle — tricuspid valveor apex Right atrium — low or near tricuspid valve Right atrium — mid Right atrium — high SVC — low — near junction with RA

SVC — high — near junction with innominate vein IVC — high — just at or below the diaphragm Left ventricle

Aorta - distal to insertion of ductus

Abbreviations: SVS and IVC, superior and inferior vena cavae RA, right atrium: RV, right venricule PA, pulmonary artery

10 VSD, ventricular septal defect TA, tricuspid regurgitation PDA, patient ductus arteriosus RP, pulmonic regurgitation ASD, atrial septal defect SBFI, systemic blood flow index

Qp/Qs, pulmonary to systemic flow ration. To perform an oximetry run, an end hole catheter like Swan-Ganz balloon floatation catheter is used, and is positioned in the left or right pulmonary artery. Cardiac output is measured by the Fick method.

Calculation of Pulmonary Blood Flow (Qp)

Pulmonary blood flow is calculated by the formula:

O2 consumption (mL/min)

PV O2 PV O2 content content (mL/L) (mL/L)

Note that if the pulmonary vein has not been entered, systemic arterial oxygen content may be used, if systemic arterial oxygen saturation is > 95 per cent.

If the systemic oxygen saturation is < 95 per cent, it is necessary to determine the presence of a R Æ L shunt.

Calculation of Systemic Blood Flow (Qs)

The following formula is used for calculation of systemic blood flow:

O2 consumption (mL/min)

SA O2 MV O2 content content (mL/L) (mL/L)

Mixed Venous Oxygen Content (MVO2) For Mixed Venous Oxygen content, the formula validated by Flamm and associates is used:

3 SVC O2 + 1 IVC O2 4 Calculation of Left to Right Shunt

The formula used for calculation of left to right shunt is:

L Æ R Shunt = Qp - Qs (L/min)

11 Flow Ratio

The ratio of Qp/Qs gives us the important physiologic information of the magnitude of left to right shunt.

Qp (SA O2 - MV O2

Qs ( PV O2 - PA O2) A QP/Qs value of <1.5 signifies a small left to right shunt and often may not require surgical correction. However, a Qp/Qs value of e” 2 indicates a large left to right shunt requiring surgical correction. Shunts of 1.5-2 are intermediate and surgery is recommended if the operative risk is low. A shunt of <1.0 indicates the presence of right to left shunt and irreversible pulmonary vascular disease.

Bidirectional Shunts

The formula used for calculating bidirectional shunts is:

O2 consumption (mL/min)

PV O2 MV O2 content content (mL/L) (mL/L)

The approximate left to right shunt is Qp – Q eff and the approximate right to left shunt is Qs – Qeff Check Your Progress 2 1) How do you use the values in blood sampling to diagnose a left to right shunt in a ventricular septal defect?

......

2) How do you use the values in blood sampling to diagnose a bidirectional shunt in a ventricular septal defect?

......

12 6.7 CORONARY ANGIOGRAPHY

Diagnostic coronary angiography has become one of the primary components of cardiac catheterization. In a coronary angiogram, the details of individual coronary anatomy are recorded, anatomic or functional pathology, thrombosis, congenital anomalies or focal spasm and also the presence of intercoronary and intracoronary collaterals. Despite many advances in non-invasive imaging, selective coronary angiography remains the “gold standard” for coronary imaging. Techniques The coronary angiogram can be performed by two approaches: 1) The femoral approach 2) The brachial/radial approach 1) The Femoral Approach This approach involves the insertion of a catheter over a guidewire i.e. inserted into a sheath in the right femoral artery. Systemic anticoagulation is used (heparin). A series of preformed catheters are employed for the procedure – commonly the Judkins left and right catheter and the pigtail catheter though a host of other catheters are available for individual anatomical variations. The common size of catheters used are: 5F, 6F, 7F and 8F. The 6F size is now commonly used all over the world for diagnostic adult procedures. Catheters Used

Fig. 6.2: Cateters used in coronary angiography

13 Indications for Coronary Angiography

Source: Braunwald’s Heart Disease–A Textbook of Cardiovascular Medicine, 7th edn., Zipes, Libby, Bonow and Braunwald. Procedure The catheter is inserted into the femoral sheath and advanced to the level of the left mainstem bronchus over the guidewire. After removal of the guidewire, the catheter is attached to the manifold system which is designed to permit flushing, pressure monitoring and contrast administration through its ports. The catheter is immediately double flushed – blood is withdrawn and discarded and heparinized saline flush is injected through the catheter lumen. Once the catheter has been flushed with saline solution, tip pressure should be displayed on the monitor at all times. Next the catheter is filled with contrast solution. Then the catheter is engaged into the desired coronary ostium for selective coronary angiography. The left and right coronary catheters

14 are engaged in the LAO view. The left Judkins catheter often engages the left coronary ostium with minimal manipulation. The right coronary catheter, however, requires clockwise rotation by almost 180° for engaging the right coronary ostium. If there is trouble with engaging the left or right coronary ostia, other catheters like the Amplatz catheter may be used. 2) The Brachial/Radial Approach This technique involves performing the coronary angiogram through the right brachial artery in the right ante-cubital fossa. Usually a 5F or 6F sheath is inserted and using a special catheter called the Sones catheter (designed by Dr. F. Mason Sones Jr.), the same process of cannulating the left and right coronary ostia under fluoroscopic guidance is performed. The same catheter is used for cannulating the left and right coronary ostia. Other Approaches More recently, coronary angiography by the radial approach is very popular — particularly because it has fewer complications than the brachial approach. Rarely coronary angiography may have to be performed by axillary approach in special circumstances. Coronary Anatomy The main coronary trunks can be considered to lie in one of two orthogonal planes. The anterior descending and the posterior descending coronary arteries lie in the plane of the interventricular septum, whereas the right and left circumflex trunks lie in the plane of the atrioventricular valves.

Fig. 6.3: Coronary anatomy in relation to the anatomic planes—interventricular septum and atrioventricular valves. L Main—Left main, LAD-left anterior descending, D—Diagonal, S-Septal, CX-Circumflex, OM-Obtuse marginal, RCA-right coronary artery, CB-Conus branch, SN-Sinus node, AcM-acute marginal, PD-posterior descending, PLV-posterior left ventricular

Fig. 6.4: The numeric coding and official names of the coronary segments

15 Right Coronary Artery: 1: Proximal, 2: Middle, 3: Distal, 4: Posterior descending, 5: Posteroatrioventricular, 6: first posterolateral, 7: second posterolateral, 8: third posterolateral, 9: inferior septals, 10: acute marginals. Left Coronary Artery: 11: Left Main, 12: Proximal left anterior descending, 13: Middle left anterior descending, 14: Distal left anterior descending, 15: first diagonal, 16: second diagonal, 17: septals, 18: Proximal circumflex, 19: Middle circumflex, 20: Distal circumflex, 21, 22, 23: first, second and third obtuse marginals, 23: left atrioventricular, 24, 25, 26: first, second and third posterolaterals, 27: left posterior descending, 28: Ramus intermedius, 29: Third diagonal Right Dominant Circulation: In 85 per cent of patients, the right coronary artery goes on to form the AV nodal artery, the posterior descending and posterior left ventricular branches which supply the inferior aspect of the left ventricle and interventricular septum. Left Dominant Circulation: In 8 per cent of the patients, the coronary circulation is left dominant – the posterior left ventricular, posterior descending and AV nodal arteries are all supplied by the terminal portion of the left circumflex coronary artery. Balanced Co-dominant Circulation: In 7 per cent of patients, there is a balanced system in which the right coronary artery gives rise to the posterior descending artery and then terminates and the circumflex artery gives rise to all the posterior left ventricular branches and also to a parallel posterior descending branch that supplies part of the interventricular septum. The SA nodal artery arises from the RCA in 60 per cent of cases and from the LCX in 40 per cent of cases. Grading of Stenosis and Grading of Coronary Artery Disease Multiple views are necessary to quantify coronary stenosis accurately. Further, there should be no foreshortening, no artifact and no other vessels crossing that area and obscuring the viewer’s judgment. Though the width of the vessel may appear almost normal, thinning of the contrast column will eventually give out the severity of luminal narrowing. The ability of the coronary angiogram to quantify the degree of stenosis at various points is limited by the fact that it consists of a “lumen-o-gram” in which stenosis is evaluated by comparison with the adjacent “reference” segment which is presumed to be normal and free of disease. Normal Range of Caliber of Vessels Vessel Range of Caliber Left main 4.5 + 0.5 mm Left anterior descending 3.7 + 0.4 mm Left circumflex (Dominant) 4.2 + 0.6 mm Left circumflex (Non-dominant) 3.4 + 0.5 mm

Right coronary (Dominant) 3.9 + 0.6 mm Right coronary (Non-dominant) 2.8 + 0.5 mm

By comparing the diameter of the disease free segment of the coronary artery to the size of the diagnostic catheter (6F=2mm), we can surmise that those vessels that are less that the diameter of the diagnostic catheter may, infact, be diffusely diseased.

16 Presently available data indicates that a stenosis that reduces lumen diameter by 50 per cent (hence reducing the cross sectional area by 75 per cent) is “hemodynamically significant” because it reduces the normal three to four fold flow reserve of a coronary bed. A 70 per cent diameter stenosis (90 per cent cross sectional area) eliminates any ability to increase flow above resting level. In clinical practice, the degree of stenosis is estimated visually from the coronary angiogram and consequently there is likely to be significant operator variability.

Fig. 6.5: Grading of Stenosis Accurate stenosis assessment is possible by: 1) Digital calipers 2) Computer assisted algorithm These techniques reduce observer variability and help to judge severity of lesions more accurately. Apart from the severity of the lesion, lesion morphology is another important parameter of assessment. The following characteristics should be looked for: 1) Eccentricity 2) Ulceration 3) Thrombus 4) Calcification 5) Dissection 6) Physiologic significance of the lesion direct flow or distal pressure measurement may be necessary for this parameter to be assessed. In fact less severe (50 per cent) lesions may be more dangerous because they have a larger lipid core and thinner fibrous cap. Coronary Angioplasty The concept of coronary angioplasty – enlargement of the lumen of a stenotic vessel by a catheter technique was first proposed by Dotter and Judkins in 1964. The concept was to advance a guidewire over a stenotic lesion. This would serve as a rail over which progressively larger

17 inflatable non-elastic balloons could be passed and the lesion could progressively be dilated till the lumen of the narrowed segment of the coronary artery is opened. The first percutaneous coronary angioplasty was performed on a conscious patient on Sept. 16, 1977. The success rate of PTCA is 98 per cent and the requirement for emergency CABG is 1 per cent and procedural mortality is 1 per cent. Much of the success of the technique is due to improvements in technology, stents, and advancements in anticoagulant and antiplatelet therapy.

Fig. 6.6: Coronary angioplasty Components of an Angioplasty System 1) Guiding catheter: The ideal guiding catheter must have a lumen diameter i.e. at least twice that of the diagnostic catheter. Current guiding catheters are available in shapes similar to the conventional Judkins and Amplatz curves as well as a wide range of custom shapes such as hockey stick, multipurpose and Voda systems for better engagement, support and balloon advancement. 2) Guidewires: Present day guidewires are “steerable” have better wire sizes (0.009 inch), tip stiffness, shaft support and lubricious coating. Modern day guidewires combine tip softness, trackability around curves, radiographic visibility, and precise torque control which allow the wire to be steered past tortuous and stenotic segments. 3) Balloons: Balloons of various sizes and compliance are used depending on operator requirement for dilation of stenotic lesions. 4) Indeflator: It is a screw powered, hand held inflation device with a pressure dial for inflating the balloon to desired levels (atmospheres) for optimum results. Mechanism of Angioplasty

Fig. 6.7: Mechanism of Angioplasty

18 Inflation of stenotic segment causes stretching of the vessel, fracture of the intimal plaque, partial disruption of the media and adventia and enlargement of the vessel lumen and outer diameter. Further, there is true plaque compression and extrusion of the contents of the plaque leading to plaque compression. Stents Stents are metallic scaffolds that are deployed within a diseased segment of a coronary artery to establish and then maintain a widely patent lumen. Stents come in various designs as shown in the diagram below:

Fig. 6.8: Types of Metallic Stents Balloon Mountable Stents Balloon mountable stents are delivered into the coronary artery in the collapsed state mounted on the balloon. The various types of balloon expandable stents are: 1) Wire coils 2) Slotted tubes 3) Modular stents Self Expandable Stents This stent is delivered into the vessel in a collapsed state constrained by an outer membrane. The moment the membrane is retracted, the stent expands inside the vessel lumen and can be balloon inflated if necessary for better results. Types of self expanding stents are: 1) Wall stent (Magic wall stent) 2) Radius stent Indications for Stenting 1) Acute or threatened closure 2) Elective stenting of Focal De-Novo Native Coronary Lesions 3) Saphenous vein graft lesions 4) Restenosis after previous angioplasty 5) Chronic total occlusion 6) Acute myocardial infarction

19 7) Long lesions 8) Small vessels 9) Aortoostial lesions 10) Bifurcation lesions 11) Intramyocardial bridging and coronary vasospasm 12) Multivessel stenting Special Stents 1) Coated stents 2) Drug eluting (Medicated) stents – reduce restenosis 3) Radioactive stents 4) Covered stents Check Your Progress 3 1) What are the two approaches for performing a coronary angiogram? ...... 2) Name two segments/branches of the right coronary artery? ...... 3) Name two segments/ branches of the Circumflex artery...... 4) What is considered a hemodynamically significant stenosis in the coronary artery...... 5) Mention any two types of stents used in coronary angioplasty......

......

20 6.8 STENOTIC AND REGURGITANT LESIONS

The normal cardiac valves offer little resistance to blood flow even when flow velocity is high. When stenosis develops, the valve orifice offers greater resistance to flow resulting in a pressure drop (pressure gradient) across the valve. At any given stenotic orifice size, greater flow across the valve produces a greater pressure gradient across the valve. Based on this concept, the Gorlin formula was derived for calculation of cardiac valve orifices from flow and pressure gradient data. Gorlin Formula Formula I: First Hydraulic Formula (Toricelli’s law) F = AVCc Where, F = flow rate A = orifice area Cc = coefficient of orifice contraction Rearranging this formula, we get: A = F VCc Wherein A is the orifice area. Formula II: Second Hydraulic Formula This relates to pressure gradient and velocity of flow: V2 = (Cv)2 2gh or V = (Cv) 2gh Wherein, V = velocity of flow Cv = coefficient of velocity g = acceleration due to gravity (980 cm/sec/sec)

h = pressure gradient in cm of H2O Combining these two equations, we get:

The final equation for calculation of valve orifice area A in cm2 is:

Where, CO = Cardiac output in cm3 / min DFP = diastolic filling period (sec/beat) (measured directly form LV/PCW/LA tracings) SEP = systolic ejection period (sec/beat) HR = heart rate (beats/min) C = empirical constant P = pressure gradient Mitral Valve Orifice Area The normal mitral valve orifice in an adult is 4-5cm2 when the valve is completely open in diastole. When the mitral valve orifice area is 1.0 cm2, then there will be a significant resting gradient across the valve and any requirement for increase cardiac output leads to an increase in

21 LA and PCW pressure and results in Pulmonary edema. This therefore, represents “critical mitral valve orifice area”. The formula for calculating mitral valve orifice area is: Where P = mean transmitral pressure gradient, and MVA = mitral valve area. Thus when the cardiac output is doubled, the transmitral gradient is quadrupled (if HR and DFP remain constant). Aortic Valve Orifice Area An aortic valve orifice area of < 0.7cm2 leads to angina, syncope or heart failure in a patient with aortic stenosis and constitutes critical aortic stenosis. The aortic valve orifice can be calculated using the formula:

Assessment of Tricuspid and Pulmonary Orifice Areas Due to the rarity of tricuspid stenosis and pulmonary stenosis, no general agreement exists on what constitutes critical orifice area in these cases. Generally a gradient of 5mmHg causes venous hypertension. In the case of pulmonary stenosis, gradients of < 50mmHg are well tolerated. Gradients of >100mmHg require intervention. Gradients between 50-100mmHg merit correction depending on the case. Alternatives to Gorlin Formula Hakki et al proposed a simplified formula for calculation of valve orifice area and had found good correlation. This formula may not be useful in substantial tachycardia. Assessment of Valvular Regurgitation The severity of valvular regurgitation is generally graded by visual assessment, although calculation of the regurgitant fraction is used occasionally. Visual Assessment of Regurgitation Valvular regurgitation may be assessed visually by determining the relative amount of radiographic contrast medium that opacifies the chamber proximal to its injection. Seller’s Classification of Regurgitation Grade of regurgitation Description + Minimal regurgitant jet seen. Clears rapidly from proximal chamber with each beat. ++ Moderate opacification of proximal chamber, clearing with subsequent beast. +++ Intense opacification ofproximal chamber, becoming equal to that of distal chamber. ++++ Intense opacification of proximal chamber, becoming denser than that of the distal chamber. Opacification often persists over the entire series of images obtained. Regurgitant Fraction A gross estimate of the degree of valvular regurgitation may be obtained by determining the regurgitant fraction (RF). Regurgitant Stroke Volume

22 It is defined as the difference between the angiographic stroke volume and the forward stroke volume. The RF is that portion of angiographic stroke volume that does not contribute to the net cardiac output. Important Formula for Regurgitant Valvular Lesions

Regurgitant stroke volume = angiographic stroke volume – forward stroke volume

RF = (Angiographic stroke volume – Forward stroke volume) Angiographic stroke volume

Forward stroke volume = Cardiac Output Heart Rate

Correlation Between Degree of Regurgitation and Regurgitant Fraction Degree of regurgitation Regurgitant fraction 1+ ? 20 per cent

2+ 21 to 40 per cent 3+ 41 to 60 per cent 4+ > 61 per cent

6.9 PERCUTANEOUS INTERVENTIONS

Over the last two decades, significant strides have been made in the field of Balloon Valvuloplasties both in terms of technique as well as equipment. Percutaneous Balloon Mitral Valvuloplasty Percutaneous balloon mitral valvuloplasty has emerged as the treatment of choice in patients with Rheumatic mitral stenosis which is rampant in developing countries. Mechanism of PBMV Mitral valvuloplasty works by the principle of “commisurotomy” — by increasing the mitral orifice area by splitting the fused commisures. The expanding balloon splits fused commisures akin to surgical commisurotomy. Patient Selection The patients who are suitable for balloon mitral valvuloplasty are: 1) Patients who are symptomatic with a mitral orifice area as determined by echocardiography and haemodynamics studies to be <1.5cm2 2) Patients with pulmonary hypertension, severe mitral stenosis and variable LV function with anatomically suitable valve 3) Patients with mitral Restenosis after previous surgical commisurotomy in anatomically suitable valves 4) Younger the patient, better the results as older patients have fibrotic valves 5) Suitable procedure for pregnant women with mitral stenosis

23 6) Life saving procedure in patients of mitral stenosis in pulmonary edema or cardiogenic shock Contraindications to Mitral Valvuloplasty 1) Left atrial thrombus 2) Moderate or greater (2+) mitral regurgitation 3) Concomitant severe coronary artery disease Anatomic Factors in Patient Selection for Mitral Valvuloplasty The ideal patient is young, has pliable non calcified mitral leaflets, and mild subvalvular disease. TEE may be necessary to exclude LA thrombus and significant mitral regurgitation pre- procedure. Massive valvular calcification and bicommisural calcification are obviously contraindications for the procedure The echocardiographic scoring system by Wilkins et al is very helpful to decide an anatomically suitable valve for Mitral Valvuloplasty. The maximum score is 16. A score of < 8 generally gives excellent results. Echocardiographic Scoring System (Wilkins’ et al.)

Parameter Description Score

Leaflet Mobility Highly mobile valve with restriction of 1 only the leaflet tips

Midportion and base of leaflets have 2 reduced mobility

Valve leaflets move forward in diastole 3 mainly at the base

No or minimal forward movement of the 4 leaflets in diastole

Valvular thickening Leaflets near normal (4-5mm) 1

Midleaflet thickening, marked thickening 2 of the margins

Thickening extends through the entire 3 leaflets

Marked thickening of all leaflet tissue 4 (8-10mm) Subvalvular thickening Minimal thickening of chordal structures 1 just below the valve

Thickening of chordae extending up to 2 1/3 of chordal length

Thickening extending upto the distal 3 third of the chordae

Extensive thickening and shortening of 4 all chordae extending down to the papillary muscle Valvular Calcification A single area of increased echo 1 brightness Scattered areas of brightness confined 2 to leaflet margins

Brightness extending into the 3 midportion of the leaflets

Extensive brightness through most of 4 the leaflet tissue

24 Technique of Balloon Mitral Valvuloplasty There are two basic techniques: 1) Double balloon technique 2) Inoue technique For the purpose of convenience, the Inoue technique will be described. Inoue Technique The procedure is performed by cannulation of the right femoral vein and the procedure is similar upto transseptal puncture which allows access into the left atrium. Following this the transseptal puncture, a Mullins type dilator and sheath is placed in the left atrium. The patient is anticoagulated with heparin after entry into LA. A coiled guidewire is passes through the Mullins sheath into the left atrium and the mullins sheath is removed. A long dilator is used to dilate the passage into the femoral vein and inter atrial septum. The dilator is removed and the Inoue balloon is threaded over the guidewire and maneuvered into the left atrium. A “J” stylet is inserted into the balloon and manipulated so as to position the Inoue balloon across the mitral valve. The balloon is then inflated – distal portion first, pulled back gently upto the narrowest position of the valve. Then the proximal portion is inflated. Finally the waist of the balloon is inflated to effectively cause commissural splitting.

Fig. 6.9: Inoue Technique Both the immediate and long term results of balloon valvuloplasty are excellent. Complications are few and the most dreadful are hemopericardium, systemic embolization or production of severe mitral regurgitation. Balloon Pulmonary Valvuloplasty Pulmonary stenosis is a relatively common congenital heart defect. Usually these children with mild to moderate pulmonary stenosis survive into childhood. Since bicuspid pulmonary stenosis is infrequent (< 20 per cent) and heavy calcification uncommon, pulmonary stenosis is well suited for balloon pulmonary valvuloplasty. Classification of Severity of Pulmonary Stenosis

Severity to PS Transvalvular Gradient Mild PS < 50 mmHg Moderate PS 50 - 100 mmHg

25 Severe PS > 100 mmHg Technique Right heart study is done to measure the transvalvular gradient and exclude supravalvular and subvalvular components. A 5F sheath is placed in the right femoral artery for pressure monitoring and an 8F sheath is placed in the right femoral vein for the BPV procedure. An RV angiogram is performed in AP and lateral views to assess location of PV and for sizing of the pulmonary annulus. It is often necessary to oversize the balloon 25 to 30 per cent larger than the valve annulus diameter. In general balloon pulmonary valvuloplasty procedure is indicated if the resting peak systolic pressure exceeds 40mmHg. Lateral projection is best suited for the procedure. An end hole catheter is positioned into the left pulmonary artery. An exchange length guide wire is anchored in distal LPA. A double balloon technique is recommended if pulmonary annulus exceeds 18-19mm, or if the single balloon catheter required for the procedure is too large for introduction into the patient’s femoral vein. With double balloon technique, the balloon diameter sum is 60 per cent more than the annulus diameter. The balloon valvuloplasty catheter is advanced across the valve and positioned with the valve in the midportion of the balloon. The valvuloplasty balloon or balloons are then inflated with, a mixture of saline and contrast, by hand, until the waist disappears. The procedure can be repeated if necessary for adequate pulmonary valve dilatation. The valvuloplasty catheter is removed and a wedge catheter is used to record the RV outflow tract gradient and cardiac output to document efficacy of the procedure followed by an RV angiogram. The acute and long-term results of this procedure have been very satisfying. Aortic Valvuloplasty Valvar aortic stenosis accounts for 4-6 per cent of CHD. LV Outflow Tract obstruction eventually leads to LV dysfunction and congestive heart failure. Congenital AS, unlike PS, progresses over time. Intervention is indicated if the LVOT obstruction is severe (catheter gradient > 65mmHg), or associated symptoms like LV dysfunction, heart failure, angina, syncope or presyncope. Indications for Balloon Aortic Valvuloplasty 1) Peak systolic pressure gradient at rest of > 65mmHg. 2) Peak systolic pressure gradient at rest of 50-64mmHg with symptoms 3) Low cardiac output regardless of the gradient. Technique BAV is usually performed by the retrograde transarterial approach. Often another catheter is placed in the LV through transseptal approach to provide continuous LV pressure monitoring throughout the procedure. The AS gradient is measured before angiography from simultaneous ventricular and aortic pressure recordings. After transseptal puncture, heparin is administered to keep the Activated Clotting Time 250-300sec. The aortic valve is crossed in a retrograde manner and a pigtail catheter is positioned in LV apex. If it cannot be crossed retrogradely, it can be crossed antegradely using a transseptal catheter. An exchange length guidewire is passed from the femoral arterial sheath and is used to guide the balloon dilatation catheter across the aortic valve in a retrograde direction.

Fig. 6.10: Biplane LV angiogram is performed in 700LAO, 200 cranial angulation and frontal or RAO projections. The aortic annulus is best measured in LAO view or in echo. Valvuloplasty is performed by single or double balloon technique. Exchange length wire is passed across the aortic valve and anchored in LV apex. A balloon whose diameter is same or 1mm less than the aortic annulus is chosen. For double balloons, the sum of diameter of the balloons should not exceed 1.2 to 1.3 times the aortic annulus. The balloon/balloons are inflated across the aortic valve until the waist disappears. Aortic root angiogram is performed post procedure to assess aortic regurgitation. Check Your Progress 4 1) What is Sellers classification of valvar regurgitation? ...... 2) How do grade severity of pulmonary stenosis from the transvalvar gradient...... 6.10 LET US SUM UP

Although there is progressive improvement in non-invasive techniques, cardiac catheterization remains a key clinical tool for assessing the anatomy and physiology of the heart and it’s associated casculature. In this unit, we discussed about the cardiac catheterization and angiography. Describing the various type of angiography such as coronary angiography,

27 pulmonary angiography, ventriculographyand aortography. We have tried to describe the various techniques of angiography, their indications and contraindications.

6.11 ANSWERS TO CHECK YOUR PROGRESS

Check Your Progress 1 1) 5-12 mm Hg 2) 15-30 mm Hg Check Your Progress 2 1) An oxyen step up in the right ventricle as compared to the preceding chamber —the right atrium. 2) An oxyen step up in the right ventricle as compared to the preceding chamber —the right atrium along with arterial desaturation indicating a right to left shunt. Check Your Progress 3 1) The Coronary angiogram can be performed by two approaches: a) The femoral approach b) The Brachial / Radial approach

2) • Proximal

• Posterior descending,

3) • Proximal circumflex,

• Middle circumflex, 4) Presently available data indicates that a stenosis that reduces lumen diameter by 50 per cent (hence reducing the cross sectional area by 75 per cent) is “hemodynamically significant” because it reduces the normal three to four fold flow reserve of a coronary bed.

5) • Coated stents

• Drug eluting (Medicated) stents – reduce restenosis Check Your Progress 4

Grade of Description regurgitation + Minimal regurgitant jet seen. Clears rapidly from receiving chamber with each beat. ++ Moderate opacification of receiving chamber, clearing with subsequent beats. +++ Intense opacification of receiving chamber, becoming equal to that of distal chamber ++++ Intense opacification of receiving chamber, becoming denser than that of the “pumping” chamber. Opacification often persists over the entire series of images obtained.

Severity of PS Transvalvular Gradient Mild PS < 50 mmHg Moderate PS 50 – 100 mmHg Severe PS > 100 mmHg