Genesis of the restrictive filling pattern: Pericardial constraint or myocardial restraint

Background: Restrictive filling pattern has been predictive of heart failure in patients with cardiomyopathy and after myocardial infarction, and is similar to the filling pattern in constrictive pericarditis and amyloid heart disease. The purpose of this study was to determine the role of both myocardial restraint and pericardial constraint in a chronic left ventricular dysfunction model with restrictive filling. Methods: After instrumentation, a flat balloon containing a high-fidelity pressure catheter was inserted through a pericardial incision in 12 dogs with chronic left ventricular dysfunction. Intracardiac volume (ICV) was manipulated by inferior venal caval balloon occlusion and volume loading while hemodynamics, echo-assessed chamber size, and transmitral Doppler were obtained at the same atrial paced rate with an intact pericardium and after pericardiectomy. Results: With an intact pericardium, deceleration time increased with reduced ICV (130 +/- 35 vs 153 +/- 47 milliseconds, P < .05) and shortened with increased ICV (107 +/- 45 milliseconds, P < .05). The filling fraction at one-third of diastole decreased with reduced ICV (45.6 +/- 29.3 vs 24.2 +/- 15.8%, P < .01) and increased with increased ICV (60.1 +/- 14.8%, P < .05). Deceleration time could be predicted from intrapericardial pressure, the transmural left ventricular chamber stiffness constant, and filling fraction at one-third of diastole. After pericardiectomy, deceleration time also shortened with increased ICV (141 +/- 26 vs 112 38 milliseconds, P < .01). However, filling fraction at one-third of diastole was markedly reduced at paced baseline (19.9 +/- 14.4%, P < .01) and with increased ICV (15.5 +/- 11.8%, P < .001) as compared with an intact pericardium. Conclusions. Pericardial constraint and myocardial restraint play a role in restrictive filling pattern. Pericardial constraint becomes evident with redistribution of diastolic filling to later in diastole after pericardiectomy.