Praecordial accelerometry: an indirect assessment of left ventricular performance

Non-invasive assessment of left ventricular response to Valsalva manoeuvre in normal and diabetic subjects using praecordial accelerocardiography

The left ventricular response to the Valsalva manoeuvre was studied in 5 normal subjects (group 1), 6 diabetics without autonomic neuropathy (group 2), and 5 diabetics with autonomic neuropathy (group 3), using the maximum amplitude of the praecordial accelerocardiogram (DE) as a noninvasive index of left ventricular performance. During the Valsalva manoeuvre DE decreased in all 3 groups. In groups 1 and 2, DE increased significantly above the control value after release of the manoveuvre (DE overshoot) but this did not occur in group 3. It is suggested that the overshoot of DE in groups 1 and 2 reflects an increase in left ventricular contractility after release of the Valsalva manoeuvre and the absence of an overshoot in DE in the patients with autonomic neuropathy is the result of loss of cardiac adrenergic innervation. The ability to detect an abnormal cardiovascular response to the Valsalva manoeuvre using the non-invasive technique of praecordial accelerocardiography may be of practical value in the assessment of left ventricular function.

The effects of exercise on the amplitude of the first heart sound in normal subjects

The cardiovascular responses to isometric and dynamic exercise have been studied in six normal subjects, before and after intravenous propranolol, using the amplitude of the first heart sound (S1), measured from an ultra-low frequency phonocardiogram, as an index of left ventricular mechanical performance. Dynamic exercise caused significant increases in heart rate and S1 amplitude which were largely inhibited by beta-adrenergic blockade. Isometric exercise also produced increases in heart rate and blood pressure, but a decrease in S1 amplitude. Propranolol had no significant effect on the cardiovascular response to isometric exercise. These results confirm previous suggestions that, in contrast to dynamic exercise, the normal cardiovascular responses to isometric exercise are relatively independent of the beta-adrenergic nervous system. Possible reasons why the improvement in left ventricular performance, which has previously been shown to occur during isometric handgrip, was not reflected in the phonocardiogram, are also discussed.

Effects of sustained isometric handgrip on praecordial accelerocardiogram in normal subjects and in patients with heart disease

The effects of isometric exercise on the maximum amplitude of the praecordial accelerocardiogram (as represented by the DE deflection) have been compared in 6 normal subjects (group 1), 12 patients with aortic stenosis (group 2), and 16 patients with myocardial disease (group 3). Whereas the tachycardia and pressor effects of isometric exercise were identical in all three groups, the normal subjects showed a significant decrease in DE during handgrip of 10 +/- 4 per cent (P less than 0.05) as compared with the insignificant increases of 8.5 +/- 6 per cent (P greater than 0.5), and 4 +/- 3.5 per cent (P greater 0.3) observed in the patients in groups 2 and 3. This response in the normal subjects differed significantly from the responses observed in the patients in groups 2 (P less than 0.02) and 3 (P less than 0.01). Of the patients in each of groups 2 and 3, 50 per cent responded abnormally to handgrip in that they showed a significant increase in DE. In the patients with aortic stenosis this subgroup of patients differed from the remainder in that they had a higher resting cardiac index (P less than 0.05). In the patients with myocardial disease this subgroup was characterized by a significantly lower resting left ventricular end-diastolic pressure (P less than 0.02). It seems, therefore, that those patients who increase DE in response to handgrip tend to have better left ventricular function at rest than those who do not. We suggest that this may be because of increased beta adrenergic activity at rest and during isometric exercise in the subgroup who respond to handgrip with an increase in DE.