Systolic pulmonary artery pressure and heart rate are main determinants of oxygen consumption in the right ventricular myocardium of patients with idiopathic pulmonary arterial hypertension.
OBJECTIVE
Increased afterload in idiopathic pulmonary arterial hypertension (IPAH) causes right ventricular (RV) hypertrophy and failure. Since RV remodelling occurs with alterations in RV oxygen metabolism, increasing our understanding in the factors determining RV O(2) consumption in IPAH is necessary. In the left ventricle, it is known that heart rate and systolic blood pressure are the main determinants of myocardial O(2) consumption (MVO(2)). However, the normal right heart has lower oxygen extraction and perfusion than the left myocardium, and RV energy metabolism is changed in hypertrophy. Therefore, it is not obvious that the relationsships of pressure and heart rate to MVO(2) hold for the overloaded human right heart. We hypothesize that systolic pulmonary artery pressure (PAP) and heart rate (HR) are the major determinants of RV MVO(2) in IPAH.


RESULTS
In 18 IPAH patients (New York Heart Association class II and III), RV MVO(2) was determined using positron emission tomography and (15)O tracers. PAP and HR were measured during right heart catheterization. RV MVO(2) was found to be related to systolic PAP (R(2) = 0.54, P < 0.001), and inversely to stroke volume (R(2) = 0.32, P = 0.015) and HR (R(2) = 0.32, P = 0.014). Relationships of MVO(2) to the rate pressure product (RPP), i.e. systolic pressure × HR, and wall stress were R(2) = 0.55, P < 0.001, and R(2) = 0.30, P = 0.020, respectively. Multiple regression of MVO(2) on HR and systolic PAP gave R(2) = 0.59, P = 0.001.


CONCLUSIONS
Systolic PAP and HR are the major determinants of RV MVO(2) in IPAH. A further increase of HR and PAP with IPAH progression suggests a compromised RV myocardial oxygen availability.
Department of Pulmonology, VU University Medical Center, De Boelelaan 1117, Amsterdam, The Netherlands.
Yeun Ying
YY
Wong
Nico
N
Westerhof
Gerrina
G
Ruiter
Mark
M
Lubberink
Pieter
P
Raijmakers
Paul
P
Knaapen
J Tim
JT
Marcus
Anco
A
Boonstra
Adriaan A
AA
Lammertsma
Willem J
WJ
van der Laarse
Anton
A
Vonk-Noordegraaf
D006328:Cardiac Catheterization; D065627:Familial Primary Pulmonary Hypertension; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology*; D006352:Heart Ventricles / Q000378:metabolism / Q000503:physiopathology*; D006801:Humans; D006976:Hypertension, Pulmonary / Q000175:diagnosis / Q000378:metabolism / Q000503:physiopathology*; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D049268:Positron-Emission Tomography; D011379:Prognosis; D011651:Pulmonary Artery / Q000503:physiopathology*; D011669:Pulmonary Wedge Pressure / Q000502:physiology*; D012189:Retrospective Studies; D013318:Stroke Volume; D013599:Systole; D013997:Time Factors; D014655:Vascular Resistance