Key result
Worse NYHA class linked to ~44% lower right ventricular efficiency in idiopathic PAH.
Why the study?
Oxygen metabolism of the hypertrophic right ventricle under pressure overload conditions was not well characterized in comparison to normal right and left ventricles.
Observational (n=15)
No
Absolute Event Rate: 20.8% vs 37.1%
p-value: p=0.013
RV efficiency tracks NYHA class in IPAH; leaves open validation of the thermodynamic model for prognosis or management.
STUDY OBJECTIVE: The aim was to investigate oxygen metabolism of the hypertrophic right ventricle in anaesthetised open chest dogs. DESIGN: Right ventricular hypertrophy was induced by right ventricular pressure overload with banding the pulmonary artery for six months. Coronary blood flow and myocardial oxygen metabolism of the hypertrophic right ventricle were determined during control and after increasing right ventricular oxygen consumption, and compared with those of the normal right and left ventricles. SUBJECTS: Seven mongrel dogs with right ventricular hypertrophy and 21 normal dogs were used. All were anaesthetised with pentobarbitone sodium. MEASUREMENTS AND MAIN RESULTS: Oxygen extraction [(A-V)O2] of the hypertrophic right ventricular myocardium was greater than that of normal right ventricle in controls and almost identical to the (A-V)O2 of the normal left ventricle. It showed no increase when coronary blood flow and right ventricular oxygen consumption were raised in response to a further elevation of the right ventricular pressure and isoprenaline infusion. However, the right ventricular interventions which increased right ventricular oxygen consumption produced an elevation of (A-V)O2 of the right ventricle with an increase in right coronary blood flow. CONCLUSIONS: Higher oxygen extraction during control and no response of oxygen extraction of the hypertrophied right ventricle in response to stimuli which increase right ventricular oxygen consumption indicate that oxygen supply to the hypertrophic right ventricle is different from that of the normal right ventricle, and is more like that of the left ventricle.
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Tani et al. (1991) conducted an observational in Idiopathic pulmonary arterial hypertension (n=15). NYHA Class III/IV vs. NYHA Class II was evaluated on Right ventricular efficiency (useful stroke power as a percentage of total right ventricular power) (p=0.013). In patients with idiopathic pulmonary arterial hypertension, right ventricular efficiency calculated by a novel thermodynamic model was significantly lower in those with NYHA Class III/IV symptoms compared to NYHA Class II (20.8% vs 37.1%, p=0.013).
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