Handgrip-induced negative U-wave in electrocardiogram of hypertensive subjects

To study clinical significance and possible mechanism of negative U-wave observed in hypertensive patients, we applied handgrip test (HG) to 35 patients with hypertension and 20 age-matched normal subjects. HG was sustained for 3 min at 50% of maximum voluntary contraction. ECG recording and measurement of blood pressure were made before, during, and after HG. During HG, systolic blood pressure was 188.7 +/- 3.4 mmHg (mean +/- SE) and diastolic blood pressure was 114.8 +/- 2.1 mmHg in hypertensives, while 145.3 +/- 2.6 mmHg and 93.8 +/- 1.1 mmHg in normals; the difference between hypertensives and normals was statistically significant (p less than 0.001). Incidence of HG-induced negative U-wave was 0% in normals, while 68.6% in hypertensives. In hypertensive subjects, HG-induced negative U-wave appeared in 24 of the 28 patients (85.7%) with minimum to moderate left ventricular hypertrophy shown by ECG and/or UCG findings (QRS-T angle greater than 130 degrees with left high voltage: left ventricular wall thickness greater than 12 mm). Further we recorded UCG during HG in 14 subjects. In 4 patients, negative U waves appeared simultaneously with increase in left ventricular dimension during diastole. In the remaining 10 cases that included both normals and hypertensives, however, neither increase in left ventricular end diastolic dimension nor negative U waves were observed. Thus we conclude that HG-induced negative U waves may be caused by stretch of the ventricular wall resulting from acute left ventricular volume overload.