Effect Of Weight Loss On The Ecg Of Normotensive Morbidly Obese Patients - Brief Article

Nutrition Research Newsletter, April, 2001

Substantial weight reduction produces a variety of favorable cardiac hemodynamic and structural alterations in morbidly obese persons. These include decreases in elevated central blood volume and cardiac output, reductions in systolic BP and left ventricular (LV) end-systolic wall stress, a decrease in LV chamber size, and regression of LV hypertrophy. There is little information concerning the effect of weight reduction on the ECG of morbidly obese persons. This recently published study examined the effect of substantial weight loss on a wide variety of ECG variables in morbidly obese patients.

Patients were selected from among those scheduled to undergo bariatric surgery for morbid obesity. Consecutive eligible patients were entered. Morbid obesity was defined as actual body weight twice the ideal body weight. Ideal body weight was defined as the highest weight within the normal weight range for each patient. The study consisted of 60 patients (48 men and 12 women; mean age, 37 [ or -] 7 years). A 12-lead ECG was performed at rest just prior to bariatric surgery and again at the time of maximum weight loss (4.5 [ or -] 1.1 months) following surgery. A transthoracic echocardiogram was also performed just prior to and at the time of maximum weight loss.

The results showed a substantial reduction in the frequency of low QRS voltage. Low voltage in obese subjects has been attributed to the presence of excessive chest-wall fat. This adipose accumulation is presumed to reduce the electrical signal generated by the left ventricle, resulting in lower precordial QRS voltage than is present in comparable lean individuals with similar weight. Weight loss is thought to reduce the amount of chest-wall fat, thus permitting a more accurate (higher) voltage signal to be recorded. The effect of weight loss on ECG criteria for LV hypertrophy in this study was variable. Substantial weight loss produced an increase in the frequency of diagnosed LV hypertrophy when ECG criteria for LV hypertrophy that are highly dependent on the precordial voltage. A decrease in the amount of anterior chest-wall fat may account for this observation. Substantial weight loss also resulted in a decrease in voltage in ECG criteria that are less reliant on precordial voltage. Actual regression of LV hypertrophy may account for this observation. Weight loss did not produce a significant decrease in mean left atrial dimension. Weight loss produced a dramatic decrease in the incidence of T-wave flattening in the inferior and lateral leads in this study.

In summary, substantial weight loss in normotensive morbidly obese patients produced the following ECG changes: a rightward shift in P-wave, QRS, and T-wave axes; a reduction in the frequency of low QRS voltage; a higher frequency of LV hypertrophy when ECG criteria that are highly reliant on precor-dial voltage are applied, and a lower frequency of LV hypertrophy when ECG criteria that are less reliant on precordial voltage are used; significantly lower (less negative) mean P-terminal force; and a marked decrease in the frequency of T-wave flattening in the inferior and lateral leads. The researchers concluded that substantial weight loss reverses many of the ECG alterations associated with morbid obesity.

M. Alpert, B. Terry, C. Hamm, M. Fan, M. Cohen, C. Massey, J. Painter. Effect of Weight Loss on the ECG of Normotensive Morbidly Obese Patients. Chest 119(2):507-510 (2001) [Correspondence: information not available]