Pressure-derived indices of left ventricular isovolumic relaxation in patients with hypertrophic cardiomyopathy.

Abstract

SUMMARY High fidelity measurements of left ventricular pressure were made at increasing pacing rates in 21 patients with hypertrophic cardiomyopathy and a control group of 11 patients investigated for chest pain who proved to have normal hearts. In both groups the fall in pressure during isovolumic relaxation from the point of min dp/dt approximated closely to a monoexponential, and could be described by a time constant and asymptote.The time constant shortened and the asymptote increased as heart rate rose in both groups. The time constant was longer and mi dp/dt less in the cardiomyopathy group than controls at all heart rates. In the cardiomyopathy patients min dp/dt, but not the time constant, was related to systolic pressure. During pacing, eight cardiomyopathy patients developed metabolic evidence of myocardial ischaemia, but indices of relaxation did not differ between these eight and the other 13 either at basal heart rate or the highest pacing rate.In 10 cardiomyopathy patients measurements were repeated at comparable pacing rates after propranolol (0.2 mg/kg). Left ventricular end-diastolic pressure and indices of contractility decreased after the drug, but the time constant did not change. Eight patients received verapamil (20 mg) after which there were substantial reductions in systolic pressure and contractility. Min dp/dt decreased in proportion to systolic pressure, but the time constant was unchanged. At the highest pacing rate before drug administration three patients had abnormal lactate extraction which was corrected by either propranolol (one patient) or verapamil (two patients). Despite abolition of metabolic evidence of ischaemia, relaxation did not improve.It is concluded that abnormal isovolumic relaxation is common in patients with hypertrophic cardiomyopathy, but its severity correlates poorly with other features of the disease. Abnormal relaxation is not the result of ischaemia, and pressure derived indices of relaxation do not improve after the administration of propranolol or verapamil.Impairment of left ventricular relaxation and diastolic function is common in patients with hypertrophic cardiomyopathyl-5 and may reflect the severity and distribution of inappropriate hypertrophy3 4 or be the result of myocardial ischaemia. I 5 Relaxation and diastolic function can improve after the administration of beta blocking drugsl 6 or verapamil.5 It is uncertain whether these drugs act directly upon the diseased myocardiums or by relieving ischaemia.IThe physiology of ventricular relaxation is poorly understood7 and its study is limited by the lack of Accepted for publication 2 August 1982 methods of quantifying isovolumic pressure fall. Min dp/dt is measured easily, but describes only one point during relaxation, and because it depends upon systolic pressure8 is of little use in comparing patients or investigating drugs that change arterial pressure. The fall in left ventricular pressure from the point of min dp/dt until mitral valve opening approximates to a monoexponential so that the rate...

Noninvasive Assessment of Left Ventricular Diastolic Function by Color M-Mode Doppler Echocardiography

“…Based on several previous studies showing that Tau is prolonged in hypertrophic cardiomyopathy (HCM), it has been believed that diastolic abnormality is one of the most important pathological features of this disease [1,2,19]. However, the conventional noninvasive parameters have failed to reflect Tau in HCM patients.…”

“…The recording of left ventricular pressure curve, using a high-fidelity tip manometer enables, can measure the time constant of isovolumic pressure decay (Tau). This parameter is hardly influenced by systolic pressure or preload, and has been used as a standard index of left ventricular relaxation [1], [2]. In addition, left ventricular volume change also reflects diastolic function and can be directly or indirectly measured through invasive cine-ventriculography [3], radionuclide ventriculography [4], M-mode echocardiography [5] and pulsed-Doppler technique [6]- [8].…”

Determinants of LV diastolic function during atrial fibrillation: beat-to-beat analysis in acute dog experiments

“…Third, it is generally accepted that is a more reliable diastolic index than dP/dt min because it is not influenced by preload or afterload and is derived from multiple pressure measurements throughout the entire period of isovolumic relaxation (8). Furthermore, the LV relaxation determined by (in contrast to dP/dt min ) was reported to be independent of systolic pressure (7,22). This seeming discrepancy with our results most likely reflects the fact that the above studies were performed during sinus rate but not AF.…”

Characterization of Intracellular Ca2+ Transient by the Hybrid Logistic Function in Aequorin-Injected Rabbit and Mouse Papillary Muscles

“…RMS was calculated as the residual sum of squares (RSS) divided by the residual degrees of freedom, which indicates the number of data points (n) analyzed minus the number of parameters (k) in the function [16,17]. The better-fit function was selected between the HL and PE functions with the adjusted coefficient of determination, r squares, (adjusted r 2 ), and Akaike information criterion (AIC), which estimate goodness of fit between functions with a different number of parameters.…”