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Seventeen patients with hypertrophic obstructive cardiomyopathy, were studied using non-invasive techniques before and after the intravenous injection of 5 mg propranolol. The following were analysed: left ventricular ejection time index, derivedfrom the carotid pulse and heart rate; the isovolumic relaxation time, derived from the apex cardiogram andphonocardiogram; the diastolic closure rate of the mitral valve; and left ventricular diameters, systolic and diastolic, both measured by echocardiography.Propranolol produced shortening of the isovolumic relaxation time, increase in both the diastolic closure rate of the mitral valve and left ventricular systolic and left ventricular diastolic diameters. These results show that propranolol increases the rate offilling and the volume of the left ventricle, indicating that an improvement in distensibility is produced by beta-adrenergic blockade.Since the first description of hypertrophic obstruc-HOCM, using simple bedside non-invasive techtive cardiomyopathy (HOCM) or idiopathic hyper-niques, and see if these methods are sensitive trophic subaortic stenosis (Brock, 1957; Braunwald enough The acute effects of beta-adrenergic blockade HOCM. Eleven were women and six men. The with propranolol in HOCM suggest that it pro-diagnosis was proven by previous catheterization duces an improvement in distensibility and filling and angiocardiography. All patients stopped propranolol therapy 4 to 7 Propranolol has been thought to be the treatment days before the investigation, which was carried of choice (Hubner et al., 1973). out in the early afternoon with the patient lying Because most drug studies involve using invasive supine. techniques, they are not applicable for the repeated assessment of patients, and therefore the beneficial Non-invasive studies effects of propranolol in HOCM must be judged These were recorded using a 6-channel Cambridge mainly by symptomatic assessment of the patient Machine (model 72112, Cambridge Scientific In- (Cohen and Braunwald, 1967;Hubner et al., 1973). struments, England), at a paper speed of 100 mmThe purpose of the present paper is to study the per second. The sensitivity settings of the control acute effect of propranolol (5 mg intravenously) in study were used in the post-propranolol state.

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1. Initial unsuccessful attempts to evaluate ventricular function in terms of the 'heart as a pump' led to focusing on the 'heart as a muscle' and to the concept of myocardial contractility. However, no clinically ideal index exists to assess the contractile state. The aim of the present study was to develop a mathematical model to assess cardiac contractility. 2. A tri-axial system was conceived for preload (PL), afterload (AL) and contractility, where stroke volume (SV) was represented as the volume of the tetrahedron. Based on this model, 'operative' contractility ('OperCon') was calculated from the readily measured values of PL, AL and SV. The model was tested retrospectively under a variety of different experimental and clinical conditions, in 71 studies in humans and 29 studies in dogs. A prospective echocardiographic study was performed in 143 consecutive subjects to evaluate the ability of the model to assess contractility when SV and PL were measured volumetrically (mL) or dimensionally (cm). 3. With inotropic interventions, OperCon changes were comparable to those of ejection fraction (EF), velocity of shortening (Vcf) and dP/dt-max. Only with positive inotropic interventions did elastance (Ees) show significantly larger changes. With load manipulations, OperCon showed significantly smaller changes than EF and Ees and comparable changes to Vcf and dP/dt-max. Values of OperCon were similar when AL was represented by systolic blood pressure or wall stress and when volumetric or dimensional values were used. 4. Operative contractility is a reliable, simple and versatile method to assess cardiac contractility.