Coronary perfusion pressure (CPP) is the pressure gradient responsible for coronary and, thus, myocardial perfusion; this ensures myocardial oxygen delivery. Maintaining CPP is vital because rates of myocardial oxygen extraction are the highest of any organ at approximately 70 to 80% under resting conditions; augmentation of coronary flow by either increasing coronary perfusion pressure or inducing coronary vasodilation are therefore the predominant means for increasing myocardial oxygen supply. If coronary perfusion is inadequate myocardial ischemia and ensuing infarction result, the incidence of which is approximately 790,000 per year in the United States.
This article aims to:
- 1) Define CPP and describe from which pressures it is derived
- 2) Explain how CPP contributes to coronary blood flow
- 3) Explain how CPP becomes altered in cardiac disease
- 4) The role of reduced CPP in type 2 myocardial infarction
- 5) Therapeutic modification of CPP in cardiovascular disease
CPP in the left ventricle is established by the pressure gradient between the aortic diastolic blood pressure and the left ventricular end-diastolic pressure (LVEDP) :
Coronary Perfusion Pressure (CPP) = Aortic Diastolic Pressure – Left Ventricular end-diastolic Pressure (LVEDP)
CPP is based on diastolic pressures because the left ventricular myocardium gets perfused during diastole rather than systole. The right and left coronary arteries both originate from the coronary sinuses at the aortic root prior to division into the right coronary and left circumflex and anterior descending arteries ; therefore, the pressure which drives coronary flow derives from the aortic root. These arteries extend along the epicardial surface before branching through the myocardium to form subendocardial plexuses to perfuse the myocardium. Because these vessels traverse the myocardium, myocardial contraction during systole compresses arterial branches and prevents perfusion. Therefore, coronary perfusion occurs during diastole rather than systole. LVEDP is subtracted from aortic diastolic pressure because coronary blood flow occurs from epicardial to endocardial regions.
While high left ventricular pressures are required to drive systemic circulation, the right ventricle generates lower pressures to perfuse the pulmonary circulation. Therefore, the right ventricular pressures are far lower than the pressures exerted by the left ventricle. Right ventricular perfusion occurs predominantly in systole because systolic aortic pressure exceeds systolic right ventricular pressure. The right ventricle is also perfused to a lesser degree in diastole when aortic diastolic pressure exceeds right ventricular end-diastolic pressure by a smaller differential.