Valsalva maneuver: a test of the functional state of cardiac innervation in Chagasic myocarditis.

The ratio between maximal and minimal R-R intervals measured during the Valsalva maneuver is an adequate means of studying the functional state of the cardiac parasympathetic nervous system. We studied the changes in heart rate evoked during the Valsalva maneuver in 49 asymptomatic Chagasic patients with different degrees of myocardial involvement. The Chagasic patients were divided in three groups. Twelve patients had no evidence of heart disease except for an abnormal myocardial biopsy. Sixteen patients had a normal electrocardiogram but revealed evidence of localized myocardial damage as shown by left ventricular cineangiography. Twenty-one patients had abnormal electrocardiograms and revealed multiple areas of abnormal left ventricular wall motion. The Valsalva ratio (mean +/- standard error) was 1.62 +/- 0.12 for controls, 1.52 +/- 0.10 for those with an abnormal biopsy, 1.48 +/- 0.06 for those with localized myocardial damage, and 1.31 +/- 0.04 for those with an abnormal electrocardiogram. There were no statistically significant differences between the control group (normal sero-negative subjects) and those patients with normal electrocardiograms. Results in those with an abnormal electrocardiogram, however, were statistically different (P less than 0.05) from the other groups. These results are in discordance with the commonly accepted hypothesis that cardiac parasympathetic denervation causes a dilated myocardiopathy in patients with chronic Chagasic myocarditis.