Coronary perfusion pressure

Coronary Perfusion Pressure

Coronary vessels with annotated arteries

Coronary perfusion pressure (CPP) is a critical physiological parameter that refers to the pressure gradient driving blood flow to the myocardium, the muscular tissue of the heart. It is essential for maintaining adequate oxygen and nutrient delivery to the heart muscle, especially during periods of increased demand or reduced supply, such as during exercise or myocardial ischemia.

Definition

Coronary perfusion pressure is defined as the difference between the aortic diastolic pressure and the left ventricular end-diastolic pressure (LVEDP). Mathematically, it can be expressed as:

CPP = Aortic Diastolic Pressure - LVEDP

This equation highlights the importance of both the aortic diastolic pressure, which provides the driving force for coronary blood flow, and the LVEDP, which represents the back pressure opposing this flow.

Physiology

The coronary circulation is unique in that it receives the majority of its blood flow during diastole, the phase of the cardiac cycle when the heart muscle relaxes. During systole, the contraction of the heart muscle compresses the coronary vessels, reducing blood flow. Therefore, the diastolic pressure is a crucial determinant of coronary perfusion.

The heart's demand for oxygen is met by increasing coronary blood flow, as the myocardium extracts a high percentage of oxygen from the blood even at rest. Any factor that reduces CPP, such as a decrease in aortic diastolic pressure or an increase in LVEDP, can compromise myocardial oxygen delivery and lead to ischemia.

Clinical Significance

Coronary perfusion pressure is a vital consideration in various clinical scenarios, including:

• **Cardiac arrest**: During cardiopulmonary resuscitation (CPR), maintaining adequate CPP is crucial for successful resuscitation and return of spontaneous circulation.
• **Heart failure**: Elevated LVEDP in heart failure can reduce CPP, exacerbating myocardial ischemia.
• **Coronary artery disease**: In patients with narrowed coronary arteries, maintaining adequate CPP is essential to prevent ischemic events.

Factors Affecting Coronary Perfusion Pressure

Several factors can influence CPP, including:

• **Systemic blood pressure**: Hypotension can reduce aortic diastolic pressure, decreasing CPP.
• **Heart rate**: Tachycardia shortens diastole, reducing the time available for coronary perfusion.
• **Ventricular compliance**: Conditions that increase LVEDP, such as left ventricular hypertrophy, can reduce CPP.

Related Pages

• Coronary circulation
• Myocardial ischemia
• Cardiac cycle
• Aortic pressure