Morphological Abnormalities in Baseline Ecgs in Healthy Normal Volunteers Participating in Phase I Studies
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Indian J Med Res 135, March 2012, pp 322-330 Morphological abnormalities in baseline ECGs in healthy normal volunteers participating in phase I studies Pooja Hingorani, Mili Natekar, Sheetal Deshmukh, Dilip R. Karnad, Snehal Kothari, Dhiraj Narula & Yash Lokhandwala Research Section, Quintiles Cardiac Safety Services, Mumbai, India Received September 30, 2010 Background & objectives: Morphological abnormalities in 12-lead electrocardiograms (ECGs) are seen in subgroups of healthy individuals like athletes and air-force personnel. As these populations may not truly represent healthy individuals, we assessed morphological abnormalities in ECG in healthy volunteers participating in phase I studies, who are screened to exclude associated conditions. Methods: ECGs from 62 phase I studies analyzed in a central ECG laboratory were pooled. A single drug-free baseline ECG from each subject was reviewed by experienced cardiologists. ECG intervals were measured on five consecutive beats and morphological abnormalities identified using standard guidelines. Results: Morphological abnormalities were detected in 25.5 per cent of 3978 healthy volunteers (2495 males, 1483 females; aged 18-76 yr); the presence was higher in males (29.3% vs. 19.2% in females; P<0.001). Rhythm abnormalities were the commonest (11.5%) followed by conduction abnormalities (5.9%), axis deviation (4%), ST-T wave changes (3.1%) and chamber enlargement (1.4%). Incomplete right bundle branch block (RBBB), short PR interval and right ventricular hypertrophy were common in young subjects (<20 yr) while atrial fibrillation, first degree atrioventricular block, complete RBBB and left anterior fascicular block were more prevalent in elderly subjects (>65 yr). Prolonged PR interval, RBBB and intraventricular conduction defects were more common in males while sinus tachycardia, short PR interval and non-specific T wave changes were more frequent in females. Interpretation & conclusions: Morphological abnormalities in ECG are commonly seen in healthy volunteers participating in phase I studies; and vary with age and gender. Further studies are required to determine whether these abnormalities persist or if some of these disappear on follow up. Key words Age distribution - clinical trials - electrocardiography - healthy population - sex distribution Morphological abnormalities in the 12-lead electrocardiographic abnormalities1. De Bacquer electrocardiogram (ECG) may occur in healthy et al2 found major morphological ECG changes in individuals. In 1962, Hiss and Lamb published data 5.5 per cent of 47358 working individuals between on 122,043 healthy male air force pilots aged 16 to 40 and 64 yr of age using data derived from four 50 yr; they found that 5,773 subjects (4.72%) had large epidemiological studies performed in Belgium 322 HINGORANI et al: ECG ABNORMALITIES IN HEALTHY SUBJECTS 323 over a 30 year period. Pelliccia et al studied the blood urea nitrogen, creatinine, albumin and glucose. prevalence of ECG abnormalities in 32,652 Italian Appropriate tests for viral hepatitis (IgM for hepatitis athletes; and found that 12 per cent had morphological A, antibody to core antigen for hepatitis B, hepatitis C abnormalities3. However, these subjects do not antibody) and HIV were performed. Urine examination really represent normal healthy individuals in the was done for protein, glucose, ketones, pH and population. Physical fitness of the normal population microscopy (RBCs, WBCs, epithelials, and casts). may not be comparable to that of air force personnel Subjects with history of long QT syndrome and athletes. Sustained high level of exercise results (personal or family) or other cardiac conduction in change in vagal tone, may also lead to structural disorder, or other clinically significant cardiac disease cardiac changes which may manifest in the ECG as were excluded. Only normotensive subjects having changes in rate, rhythm and QRS amplitude4,5. There resting blood pressure (>90 mm Hg and <140 mm Hg are some studies in the general population. However, systolic; >60 mm Hg and <90 mm Hg diastolic) and subjects in these studies are screened for co-morbid normal resting heart rate (>50 bpm and <100 bpm) conditions by self-reporting or by a questionnaire3. were included. Female subjects were included only On the other hand, healthy volunteers participating if they were not pregnant (negative urine pregnancy in phase I studies are screened rigorously to exclude test in women of childbearing age) or lactating. Only associated conditions. Therefore, these individuals non-smokers or subjects who did not use any tobacco/ are more likely to represent healthy individuals than nicotine products in the 6-month period preceding the those in population-based studies. screening visit were included. Individuals with a body There are two large studies on ECG intervals in mass index <18 or >30 kg/m2, those with clinically healthy individuals participating in drug studies6,7. significant abnormality at the screening medical Dmitrienko et al6 studied the reference ranges of assessment (history, physical examination, clinical the ECG intervals and heart rate in baseline ECG laboratory tests, or ECG), or history of drug or alcohol recordings from 13,039 subjects included in clinical abuse were excluded. trials. However, they did not study morphological ECG All subjects signed written informed consent forms abnormalities. Mason et al7 have reported on drug-free for the respective study protocols and were able to ECGs from 79,743 subjects in clinical trials with a focus understand and comply with the protocol requirements, on defining reference ranges for ECG intervals; in this instructions and protocol-stated restrictions. Age and study, the authors excluded 8455 (15.5%) subjects due to gender of each subject was noted. Only a single drug- presence of morphological ECG abnormalities7. Since free baseline ECG from each subject was included in there is a paucity of data from healthy individuals, we the present analysis. studied the presence of morphological abnormalities in baseline ECGs in healthy volunteers participating in ECGs were recorded using a digital drug trials. electrocardiograph (Model Eli 250, Mortara Instrument Inc, Milwaukee, WI or Model MAC5000, Material & Methods GE Medical Systems, Freiburg, Germany) and were ECG data pooled from 62 phase I studies analyzed on-screen using digital calipers (CalECG conducted globally by different pharmaceutical Version 1.3, AMPS LLC, New York). For each ECG, companies between 2005 and 2009, where Quintiles PR interval, QRS duration, RR and QT intervals was Cardiac Safety Services, Mumbai was used as a central the average of measurements made on five consecutive ECG laboratory were analyzed retrospectively. Only beats in lead II or V5. Morphology of the each ECG studies that included healthy normal volunteers were was interpreted in a standard sequence of rate, rhythm, considered. conduction abnormality, hypertrophy/enlargement, axis, and or ischaemia/infarction. Standard diagnostic In all studies, volunteers were screened by criteria were used to define various abnormalities history, physical examination and laboratory (Table I). For each ECG, the reader could enter any tests. Haematological tests included haemoglobin, number of diagnoses. haematocrit, total and differential leukocyte counts and platelet count. Blood chemistry included serum Statistical analysis: Chi-square test was used to bilirubin, transaminases, alkaline phosphatase, compare prevalence of morphological abnormalities in sodium, potassium, chloride, calcium, bicarbonate, males and females, and in various age groups. 324 INDIAN J MED RES, MARCH 2012 Table I. ECG criteria for diagnosis of morphological abnormalities Diagnosis Criteria Rhythm disturbances Sinus tachycardia26 Sinus rhythm with heart rate >100 bpm Sinus bradycardia5 Sinus rhythm with heart rate < 50 bpm Atrial extra systole: unifocal27 Atrial premature complexes originate from ectopic complexes in the atria. These may be unifocal or multifocal in origin. The P wave of the extrasystole is abnormal and different in configuration from Atrial extra systole: multifocal27 sinus P wave and is premature in relation to the basic rhythm. QRS morphology typically unchanged unless functional BBB. Incomplete compensatory pause. Ventricular extra systole: Ventricular extra systole also known as premature ventricular complex has its QRS complex that unifocal27,28 originates in the ventricles and is abnormally wide and accompanied by secondary ST-T changes. These beats are premature in relation to the expected beat of the basic rhythm. There is often a full compensatory pause following the PVC. Retrograde P wave due to retrograde ventriculo-atrial conduction may appear. PVCs originating from the same focus have constant coupling interval (interval between the PVC and the preceding beat of basic rhythm), except parasystole. According to the relation to basic beats, these may occur in various patterns such as bigeminy (relation 1:1), trigeminy (2:1), or can be in couplets when two PVCs follow in succession. Ectopic atrial rhythm5 Presence of abnormal P waves and with a heart rate between 50 - 100 bpm. Atrial fibrillation28 Complete absence of P waves. Rapid oscillation (“f” waves) may be seen varying in size, shape and timing. Irregularly irregular ventricular rhythm. Junctional premature complex28 Junctional beat occurring earlier than the expected normal sinus P wave. P wave may follow, be superimposed on or rarely precede the QRS