Right ventricular oxygen delivery as a determinant of right ventricular functional reserve during exercise in juvenile swine with chronic pulmonary hypertension

Abstract

Assessing right ventricular (RV) functional reserve is important for determining clinical status and prognosis in patients with pulmonary hypertension (PH). In this study, we aimed to establish RV oxygen (O2) delivery as a determinant for RV functional reserve during exercise in swine with chronic PH. Chronic PH was induced by pulmonary vein banding (PVB), with sham operation serving as control. RV function and RV O2 delivery were measured over time in chronically instrumented swine, up to 12 wk after PVB at rest and during exercise. At rest, RV afterload (pulmonary artery pressure and arterial elastance) and contractility ( Ees and dP/d tmax) were higher in PH compared with control with preserved cardiac index and RV O2 delivery. However, RV functional reserve, as measured by the exercise-induced relative change (Δ) in cardiac index, dP/d tmax, and end-systolic elastance ( Ees), was decreased in PH, and RV pulmonary arterial coupling was lower both at rest and during exercise in PH. Furthermore, the increase in RV O2 delivery was attenuated in PH during exercise principally due to a lower systolic coronary blood flow in combination with an attenuated increase in aorta pressure while arterial O2 content was not significantly altered in PH. Moreover, RV O2 delivery reserve correlated with RV functional reserve, Δcardiac index ( r2 = 0.85), ΔdP/d tmax ( r2 = 0.49), and Δ Ees ( r2 = 0.70), all P < 0.05. The inability to sufficiently increase RV O2 supply to meet the increased O2 demand during exercise is principally due to the reduced RV perfusion relative to healthy control values and likely contributes to impaired RV contractile function and thereby to the limited exercise capacity that is commonly observed in patients with PH. NEW & NOTEWORTHY Impaired right ventricular (RV) O2 delivery reserve is associated with reduced RV functional reserve during exercise in a swine model of pulmonary hypertension (PH) induced by pulmonary vein banding. Our data suggest that RV function and exercise capacity might be improved by improving RV O2 delivery.

Right ventricular myocardial oxygen tension is reduced in monocrotaline-induced pulmonary hypertension in the rat and restored by myo-inositol trispyrophosphate

“…Our data nicely support these observations, indicating that indeed resting myocardial pO 2 is much higher in RV than in LV. Higher extravascular compression in LV than in RV may be responsible for this phenomenon 24 .…”

Coronary blood flow in heart failure: cause, consequence and bystander

“…However, in acute right ventricular pressure overload by acute pulmonary banding in dogs, there is increased alpha-adrenergic coronary vasoconstriction, increased extravascular compression and subendocardial ischemia [ 72 , 73 ]. With chronic right ventricular pressure overload by chronic pulmonary stenosis, adenosine-recruitable coronary vasodilator reserve in the hypertrophied right ventricle is reduced particularly in the subendocardium [ 155 ] which impairs metabolic vasodilation during exercise [ 23 , 156 ]. Patients with chronic pulmonary hypertension have reduced right coronary artery blood flow in proportion to right ventricular hypertrophy [ 257 ] and reduced adenosine-recruitable coronary reserve on MRI [ 262 ].…”