Volume loading improves low cardiac output in experimental right ventricular infarction

Abstract

To evaluate the effect of volume loading in the low output state associated with right ventricular infarction, isolated right ventricular infarction was produced in seven dogs with the pericardium intact. Volume loading and pericardiotomy were then sequentially performed. After the production of right ventricular infarction, right ventricular systolic pressure decreased by 25%, aortic pressure by 36% and cardiac output by 32%. Right ventricular ejection fraction decreased by 57%, but left ventricular ejection fraction did not change significantly. Left ventricular transmural pressure and diastolic size decreased, and right ventricular diastolic size increased. Intrapericardial pressure increased and equalization of diastolic pressures was noted. Volume loading resulted in increased right ventricular systolic pressure and stroke work, increased aortic pressure and cardiac output and increased transmural pressure and diastolic size in both ventricles. Pericardiotomy resulted in further increases in right and left ventricular filling, stroke work and cardiac output, as well as resolution of equalized diastolic pressures. These results indicate that cardiac output in experimental right ventricular infarction increases with volume loading, which enhances left ventricular preload by augmenting right ventricular output. Elevated intrapericardial pressure affects filling of both ventricles and may play a role in the pathophysiology of low cardiac output in right ventricular infarction.

Acute Right Ventricular Dilatation in Response to Ischemia Significantly Impairs Left Ventricular Systolic Performance

“…Using the same model, they went on to show that the cardiac output could also be increased by volume loading and that the hemodynamic improvement could be further augmented by pericardiotomy. 4 It thus appears that the normal pericardium plays an important role in determining hemodynamics in conditions associated with acute RV dilatation. Studies of RV infarction in dogs, however, are difficult to apply to humans because the RCA in dogs does not supply the interventricular septum.…”

“…Although this hypothesis is intuitively simple and has been validated to some extent by the finding of increased LV EDPs and reduced LV transmural pressures in acute RV dilatation, 4,5 no studies to date have examined LV systolic performance in this context.…”

“…Goldstein et al 4 demonstrated in a dog model of acute RV infarction that LV pressure generation and cardiac output could be improved by both volume loading and pericardiotomy. In a dog model of acute pulmonary embolism, pericardiotomy produced a similar improvement in cardiac output, but volume loading in the presence of an intact pericardium caused rapid hemodynamic collapse.…”

Diretrizes

“…Na verdade, a hipotensão arterial grave após o uso de nitratos sublinguais é uma manifestação comum do infarto de ventrículo direito, sendo o grau da hipotensão geralmente desproporcional à gravidade eletrocardiográfica do infarto. Nessas situações, geralmente uma carga volêmica com solução salina fisiológica normaliza a hipotensão e melhora o débito cardíaco 384 . Em outros casos, porém, a sobrecarga de volume pode ocasionar elevação acentuada da pressão de enchimento do ventrículo direito e o consequente agravamento da dilatação ventricular, com redução do débito cardíaco 385 .…”

III Diretriz sobre tratamento do infarto agudo do miocárdio

“…Na verdade, a hipotensão arterial grave após o uso de nitratos sublinguais é uma manifestação comum do infarto de ventrículo direito, sendo o grau da hipotensão geralmente desproporcional à gravidade eletrocardiográfica do infarto. Nessas situações, geralmente uma carga volêmica com solução salina fisiológica normaliza a hipotensão e melhora o débito cardíaco 524 . Em outros casos, porém, a sobrecarga de volume pode ocasionar elevação acentuada da pressão de enchimento do ventrículo direito e o conseqüente agravamento da dilatação ventricular, com redução do débito cardía-co 525 .…”