H Forst1, J Racenberg, K Messmer. 1. Institut für Anaesthesiologie, Ludwig-Maximilians-Universität München, Klinikum Grosshadern.
Abstract
UNLABELLED: Impaired right ventricular (RV) performance due to increased RV afterload in patients with sepsis or acute respiratory failure has been attributed to relative hypoperfusion and myocardial ischemia of the stressed free RV wall. There is evidence from experiments, however, that the normal RV is able to respond to a pressure load with adequate increases in myocardial blood flow. Whether or not ischemia of the free wall contributes to RV failure and whether restoration of RV perfusion can improve RV performance remains to be elucidated. The aim of this study was to compare local RV contractility to parameters of global RV contractility prior to and after induction of ischemia to its free wall. METHODS: Studies were performed in a total of 16 open-chest dogs using sonomicrometry to determine local contractility (velocity and percentage of fiber shortening) in the RV inflow tract (n = 8) prior to, 5, and 30 min after acute ligation of the right coronary artery (RCA). Parameters of global RV contractility (dP/dtmax, Vmax) were derived from intraventricular pressure measurements (tip-manometer). Regional myocardial blood flow (n = 6) was determined by the radioactive microsphere technique. Furthermore, the septal-lateral diameters of the RV (n = 8) and left ventricle (LV, n = 5), as well as the anterior-posterior diameter (n = 4) of the LV were measured simultaneously by use of sonomicrometers (Fig. 1); ventricular pressure-diameter diagrams were constructed in order to assess the dynamic geometry of the heart. RESULTS: Acute ligation of the RCA resulted in a reduction of myocardial blood flow (-39% to -72%), predominantly in the RV inflow tract (Table 1). The segment length of the RV free wall and diameter of the RV increased following RCA ligation (Fig. 3a) whereas the septal-lateral diameter of the LV decreased concomitantly. The LV anterior-posterior diameter remained unaffected (Table 2, Fig. 3b). While local RV contractility (percent shortening and velocity of fiber shortening) deteriorated (-40% and -32%, respectively), the parameters of global RV contractility (dP/dtmax, Vmax) remained unchanged (Fig. 4a). Heart rate, mean arterial pressure, RV systolic pressure, and LV filling pressure remained unchanged (Fig. 4b), whereas RV filling pressure increased (+52%) and cardiac output was reduced (-13%).(ABSTRACT TRUNCATED AT 400 WORDS)
UNLABELLED: Impaired right ventricular (RV) performance due to increased RV afterload in patients with sepsis or acute respiratory failure has been attributed to relative hypoperfusion and myocardial ischemia of the stressed free RV wall. There is evidence from experiments, however, that the normal RV is able to respond to a pressure load with adequate increases in myocardial blood flow. Whether or not ischemia of the free wall contributes to RV failure and whether restoration of RV perfusion can improve RV performance remains to be elucidated. The aim of this study was to compare local RV contractility to parameters of global RV contractility prior to and after induction of ischemia to its free wall. METHODS: Studies were performed in a total of 16 open-chest dogs using sonomicrometry to determine local contractility (velocity and percentage of fiber shortening) in the RV inflow tract (n = 8) prior to, 5, and 30 min after acute ligation of the right coronary artery (RCA). Parameters of global RV contractility (dP/dtmax, Vmax) were derived from intraventricular pressure measurements (tip-manometer). Regional myocardial blood flow (n = 6) was determined by the radioactive microsphere technique. Furthermore, the septal-lateral diameters of the RV (n = 8) and left ventricle (LV, n = 5), as well as the anterior-posterior diameter (n = 4) of the LV were measured simultaneously by use of sonomicrometers (Fig. 1); ventricular pressure-diameter diagrams were constructed in order to assess the dynamic geometry of the heart. RESULTS: Acute ligation of the RCA resulted in a reduction of myocardial blood flow (-39% to -72%), predominantly in the RV inflow tract (Table 1). The segment length of the RV free wall and diameter of the RV increased following RCA ligation (Fig. 3a) whereas the septal-lateral diameter of the LV decreased concomitantly. The LV anterior-posterior diameter remained unaffected (Table 2, Fig. 3b). While local RV contractility (percent shortening and velocity of fiber shortening) deteriorated (-40% and -32%, respectively), the parameters of global RV contractility (dP/dtmax, Vmax) remained unchanged (Fig. 4a). Heart rate, mean arterial pressure, RV systolic pressure, and LV filling pressure remained unchanged (Fig. 4b), whereas RV filling pressure increased (+52%) and cardiac output was reduced (-13%).(ABSTRACT TRUNCATED AT 400 WORDS)