Non-invasive assessment of diastolic function in hypertrophic cardiomyopathy on and off beta adrenergic blocking drugs.

Abstract

SUMMARY Beta adrenergic blocking drugs in hypertrophic cardiomyopathy provide symptomatic relief but their effect on long-term prognosis is uncertain.Thirty patients were studied non-invasively by simultaneous recordings of echocardiogram, apexcardiogram, phonocardiogram, and electrocardiogram in order to assess diastolic abnormalities on and off oral beta adrenergic blocking drugs. While on treatment these patients had a mean dose of propranolol 200 mg/day. The treatment was stopped for one week and then non-invasive assessment was repeated.The following diastolic time intervals were studied: isovolumic relaxation period (A2-mitral valve opening); rapid relaxation period (A2-O point of the apexcardiogram), and the period from mitral valve opening to the 0 point of the apexcardiogram (Mo-0) when most of the filling of the left ventricle occurs. The prolongation of the rapid relaxation period reflects a reduced rate of fall of the left ventricular pressure when the pressure differential does not change between A2 and the 0 point of the apexcardiogram, and in this study this period was prolonged in 19, shortened in eight, and remained the same in three patients after beta blockade. The Mo-O point was prolonged in 22, shortened in seven, and was unchanged in one patient after beta adrenergic blocking drugs. All these results were independent of heart rate.In conclusion the response of diastolic time intervals to beta blocking drugs in hypertrophic cardiomyopathy was variable but there was a significant number of patients in whom the time available for filling of the left ventricle was prolonged, suggesting better filling possibly because of improved distensibility of the left ventricle after beta adrenergic blocking drugs.

No Influence of Heart Rate on Early Diastolic Time Intervals

“…Physiologi cally, the O point represents the point of equilibrium between the rate of relaxation and the rate of filling, at which time the pressure then starts to rise as filling con tinues [7], Our results emphasize that the EDTI are almost inde pendent of the heart rate. This finding is common in various heart diseases.…”

“…Though the EDTI are af fected by some drugs [7,14], they may be determined mainly by diastolic property due to individual diseases or disease states. In conclusion, EDTI are not affected by the heart rate in various heart diseases.…”

“…(2) The interval from MVO to the O point of the apexcardiogram (MVO-O). This phase is from the point that left ventric ular filling occurs to the turning point (O) where the rate of filling and the rate of relaxation are in equilibrium [7], In order to evaluate the effect of heart rate on EDTI, EDTI were measured over 20 cycles and the following variation rate (%) was calculated in each patient: (B -A/A) X 100 (A = EDTI at minimal R-R interval, B = maximal EDTI). The mean value of variation rate in each group was expressed as mean ± 1 SD.…”

2011 ACCF/AHA Guideline for the Diagnosis and Treatment of Hypertrophic Cardiomyopathy: Executive Summary

“…The reduction in heart rate also prolongs the diastolic filling period, which may allow for more efficient inactivation of myocardial contractile proteins, thereby improving diastolic filling. 255,256 In those patients unable to tolerate beta blockers or those with symptoms unresponsive to beta blockers, calcium channel blockers may provide effective symptomatic relief. Verapamil has been the most intensively studied such agent (Figure 4).…”

Does Isovolumic Relaxation Time Reflect the Severity of Left Ventricular Hypertrophy in Patients with Essential Hypertension?

“…With regard to the left ventricular diastolic functions, the isovolumic relaxation time (IRT) is one of the most popular and reliable indices and has been used to assess the cardiac functions in various cardiac diseases [5][6][7][8], It is well known that no significant influence of the heart rate on IRT is observed over a wide range of R-R intervals [9,10]; therefore, it is advantageous to use IRT in assess ing the changes of left ventricular function in various heart diseases.…”