sign in sign up
<<
Home , Afterload, Cardiac output, Cardiac physiology, Hemodynamics

2017-09-22

objectives cardiac function & • review the principles of electromechanical coupling • master the concept of , , and contractility

Lars Grosse-Wortmann • understand the difference between pressure and resistance • comprehend the indication of CMR in shunt lesions … or: what do contact lenses and have in common ? • speak a common language

• electro-mechanical coupling

• determinants of

• the

• hemodynamics

1 2017-09-22

1. Ca++ enters 2. binds to -C 3. binds to 4. ATP binds to myosin 5. ATP → ADP + P 6. release of P 7. power 8. release of ADP 9. ATP binds to myosin 10. muscle relaxes

• electro-mechanical coupling

• determinants of cardiac output

• the cardiac cycle

• hemodynamics Otto Frank Ernest Starling

2 2017-09-22

Frank Starling law cardiac output • CO = amount of pumped by each in one minute

• CO = rate (HR) X (SV)

• CI = CO, indexed to BSA = CO / BSA

• example: – BSA 2.0 m2 – HR 60 bpm, SV 90 ml • CO = 5.4 l/min • CI = 2.7 l/min/m2

regulation of CO factors affecting SV

• HR, SV • PRELOAD – extend of myocardial stretch by contained blood • SV = amount of blood pumped by one – ~ CVP ventricle during one contraction = EDV (enddiastolic volume) – • AFTERLOAD – load against the ventricle must pump ESV (endsystolic volume) – ~ BP

• EF = portion of EDV that is pumped during • CONTRACTILITY one contraction – of myocardial “squeeze” = SV / EDV – ~ EF

3 2017-09-22

preload or afterload ? afterload  preload

• mitral regurgitation

• pulmonary stenosis

• VSD

• ASD

• coarctation of

• H(o)CM

• PDA

which heart would you want ?

nl. DCM HCM d X Law of Laplace • What we know is not much. What we do not know is immense. • The weight of evidence for an extraordinary claim must be proportioned to its strangeness.

4 2017-09-22

contractility •  contractility from: – increased sympathetic stimuli – Ca++, positive and other drugs

•  contractility from: – – intrinsic myocardial – – – sympathetic inhibition

• EF = (EDV-ESV/EDV) x 100 • Estimates global ventricular performance • Echo: – M mode – Simpson’s – 3D echo • dependent on preload / afterload / • no information on regional wall motion, synchronicity, AV valve function

5 2017-09-22

ejection fraction M-mode ejection fraction Simpson‘s

myocardial mechanics

Courtesy of P. Claus / M. Friedberg

Courtesy of B. Eidem / M. Friedberg

6 2017-09-22

cardiac cycle

• electro-mechanical coupling 1 Late : both sets of START chambers are relaxed and ventricles fill passively.

Isovolumic ventricular 5 relaxation: as ventricles 2 Atrial : atrial contraction relax, pressure in ventricles a small amount of • determinants of cardiac output falls, blood flows back into additional blood into ventricles. cups of semilunar valves and snaps them closed.

• the cardiac cycle

• hemodynamics Isovolumic ventricular Ventricular ejection: 3 4 contraction: first phase of as ventricular pressure ventricular contraction pushes rises and exceeds AV valves closed but does not pressure in the , create enough pressure to open the semilunar valves semilunar valves. open and blood is ejected.

the cardiac cycle Time (msec) 0 100 200 300 400 500 600 700 800

Electro- QRS QRS Cardiac cycle complex cardiogram complex (ECG) P T P

120

90 Dicrotic Aorta Pressure notch (mm Hg) Left 60 ventricular Pulmonary pressure Left atrial 30 pressure Tricuspid valve ejection

S2 Heart S1 sounds 135 Left ventricular volume (mL) 65 Atrial Ventricular Ventricular Atrial

systole systole diastole systole Wigger‘s diagram Wigger‘s

Atrial systole Isovolumic Ventricular Early Late Atrial ventricular systole ventricular ventricular systole contraction diastole diastole

7 2017-09-22

the cardiac cycle the cardiac cycle

Aorta Aorta Pulmonary artery Mitral valve Mitral valve Tricuspid valve Tricuspid valve filling

isovolumetric relaxation

the cardiac cycle the cardiac cycle

Aorta diastesis Aorta Pulmonary artery Pulmonary artery Mitral valve Mitral valve Tricuspid valve filling Tricuspid valve

isovolumetric contraction

8 2017-09-22

shortens diastole

• electro-mechanical coupling

• determinants of cardiac output

Chung et al., Am J Physiol Heart Circ Physiol 287:2003-08, 2004 • the cardiac cycle

60 bpm 1000 ms • hemodynamics

150 bpm 400 ms

how do we know ... ? cardiac catheterization

2006 BC Imhotep observations on the 400 BC Hippocrates signs and symptoms of heart blood, phlegm, black bile, yellow bile 300 BC Aristotle beating heart in a chick embryo 250 BC Erasistratus anatomy of the heart with 4 valves 129-199 Galen heart is a muscle, but liver moves the blood, blood passes through pores in the septum 1540 Servetus pathway of blood, oxygenation in the 1904 - 1979 1628 Harvey heart is a pump, http://www.ptca.org/archive/bios/forssmann.html

9 2017-09-22

X-rays “Röntgen-rays“ pulmonary arterial pressure • 15 – 25mmHg / 8-12mmHg –  in • left to right shunt • PAH • pulmonary stenosis, MS, elevated LVEDP

1845 - 1923

6 L 9 L Qp / Qs • R = ΔP / Q Ohm‘s law (R=V/I) 3 L 1.5:1 – mmHg / [ml/(min x m2)] – in Wood units x m2 • Rs = (AO-P – RA-P) / Qs (15-30 WU*m2) • Rp = (PA-P – LA-P) / Qp (<3 WU*m2) 6 L 3 L 3 L – increases with acidosis, pCO2 ++ – decreases with O2, NO, (prostacyclin, Ca -block., sildenafil, bosentan)

10 2017-09-22

ways to measure Qp and Qs

• dilution (dye, heat) – Fick

1829 - 1901

14 year ♀ the MAPCA anatomy ? surgical options ? PHtn ?

I = I2-I1 = V*CI2 – V*CI1

V = I / (CI2–CI1)

V/t = I / [t*(CI2–CI1)]

CO = VO2 / (O2venous – O2arterial)

11 2017-09-22

PAPVC Qs = SVC + DAO flows 2 = 2.40 l/min/m2 • RPA = 4.0 l/min/m Qp = pulmonary vein flow • LPA = 5.0 l/min/m2 = 6.20 l/min/m2 • Qp = 9.0 l/min/m2 Qp/Qs = 2.58 • Qs = ascending aorta = 3.0 l/min/m2 r-MAPCA r-MAPCAs: inaccurate l-MAPCAs = 3.61 l/min/m2 • Qp / Qs = 3.0 RPVs = 2.16 l/min/m2 • total left-to-right shunt = 6.0 l/min/m2 r-mAP = 61mmHg, wedge 15mmHg 2 r-PVRi = 21 WU * m2 • vertical vein = 1.5 l/min/m l-mAP = 17mmHg • calculated LRS via ASD l-PVRi = 0.6 WU * m2 2 l-MAPCA • total LRS – vertical vein = 4.5 l/min/m

CHD – made simple summary how does the blood • relaxation consumes energy go ‘round ? • pulmonary blood flow • myocardial performance depends on • systemic blood flow preload, afterload, and contractility • intracardiac shunts • extracardiac shunts • blood follows the path of least resistance • path of least resistance • pressure + resistance + shunt • RV preload / afterload • LV preload / afterload • ventricular function

12