The electrocardiogram in morbid obesity

O particularly morbid obesity, is known to produce changes in cardiac morphology such as left ventricular (LV) enlargement, and eccentric LV hypertrophy and right ventricular hypertrophy.1,2 Thus, morbid obesity might also be expected to alter the electrocardiogram. Prior studies assessing the electrocardiogram in obesity have identified T-wave abnormalities in the inferior leads and trends toward leftward axis and low QRS voltage as the most common alterations.3–5 These studies assessed a limited number of electrocardiographic (ECG) variables in persons with variable degrees of obesity and did not uniformly exclude hypertensive patients or use a control group. The present study provides a comprehensive survey of ECG variables in normotensive morbidly obese subjects and normal lean controls, and determines the frequency of established ECG abnormalities in both groups. • • • Morbid obesity was defined as actual body weight equal to or more than twice the ideal body weight based on 1993 Metropolitan Life Insurance tables.6 Morbidly obese patients were selected from those undergoing clinical evaluation for bariatric surgery. The control group was selected from a pool of lean healthy normotensive subjects and was matched for age and gender. Lean body weight was defined as weight within the normal range based on 1993 Metropolitan Life Insurance tables.6 Neither the morbidly obese nor the control groups had clinical, electrocardiographic, radiographic, or echocardiographic evidence of systemic hypertension, coronary artery disease, valvular heart disease, cardiomyopathy (unrelated to obesity), pericardial disease, or congestive heart failure. Those who were not in sinus rhythm at the time of the index electrocardiogram, those with serum electrolyte disturbances, and those receiving drugs that might affect the electrocardiogram were excluded from the study. The study group consisted of 100 morbidly obese patients and 100 controls. Patient characteristics of morbidly obese subjects and controls are listed in Table I. A 12-lead resting ECG was obtained in the supine position using a standard technique with a HewlettPackard 1517 electrocardiograph (Andover, Massachusetts) with a filter setting of 100 Hz at speed of 25 mm/s. Axes were measured by hand. All electrocardiograms were interpreted by 1 investigator (MAA) on 3 separate occasions. The ECG interpreter was blinded to patient identification and clinical data. The intraobserver variability was ,2% for all variables. M-mode and 2-dimensional echocardiograms were obtained in the left lateral and supine positions using a Hewlett-Packard Sonos 1000 ultrasonograph with a 2.25-MHz transducer in accordance with American Society of Echocardiography recommendations.7 Echocardiographic measurements were obtained in accordance with American Society of Echocardiography criteria.7 Echocardiographic LV mass/height index was calculated using the formulas of Devereux and Reichek8 and Levy et al.9 Normal ranges for LV mass/height index were ,104 g/m in women and 120 g/m in men.6 ECG abnormalities assessed are listed and defined in Table II. Cardiac arrhythmias and conduction disturbances were diagnosed using previously published criteria.10,11 ECG variables were classified as categorical or continuous. Categorical ECG variables used in this study are listed in Table II. They were defined as ECG abnormalities for which specific diagnostic criteria exist. Continuous ECG variables used in this study are listed in Table III. They were defined as ECG measurements of rate, duration, or amplitude, or ratios that were not limited by specific diagnostic criteria. The chi-square test was applied to categorical data to determine if significant differences existed in the frequency of ECG abnormalities between morbidly obese and normal lean patients. The Student’s t test was used to determine if significant differences in mean values for specific continuous variables existed between morbidly obese and normal lean patients. Mean values are expressed 6 1 SD. A p value ,0.05 was considered statistically significant. • • • Table II shows the frequency of categorical variFrom the Division of Cardiology, University of South Alabama, Medical Center, Mobile, Alabama; and the Department of Surgery, University of Missouri, Columbia, Missouri. Dr. Alpert’s address is: University of South Alabama, Suite 10C, Medical Center, 2451 Fillingim Street, Mobile, Alabama 36617. Manuscript received July 28, 1999; revised manuscript received and accepted October 22, 1999. TABLE I Patient Characteristics