In managing a patient with hypertension and coronary artery disease, what determines coronary artery perfusion: diastolic blood pressure, systolic blood pressure, mean arterial pressure, pulse pressure, or ejection fraction?

Coronary Artery Perfusion in Elderly Patients with Hypertension and CAD

Coronary artery perfusion is primarily determined by diastolic blood pressure, which creates the coronary perfusion pressure gradient necessary for myocardial blood flow. 1

Physiological Basis of Coronary Perfusion

Myocardial perfusion occurs almost exclusively during diastole, making diastolic blood pressure the critical determinant of coronary perfusion pressure. This is particularly important in your 90-year-old patient with multiple cardiovascular comorbidities.

Key physiological principles:

• Coronary blood flow occurs predominantly during diastole when the myocardium is relaxed
• Coronary perfusion pressure is determined by the difference between aortic diastolic pressure and left ventricular diastolic pressure 1
• While mean arterial pressure influences overall tissue perfusion throughout the body, the coronary circulation specifically depends on diastolic pressure
• Systolic blood pressure primarily affects myocardial oxygen demand by increasing left ventricular workload 1

Clinical Implications for Your Patient

Your patient presents with several concerning features:

• High systolic pressure (>160 mmHg)
• Low diastolic pressure (<50 mmHg)
• Wide pulse pressure (>110 mmHg)
• Multiple cardiovascular comorbidities (CAD, previous stroke, HFpEF)

This combination creates a challenging clinical scenario:

1. Coronary perfusion risk: The low diastolic pressure (<50 mmHg) may compromise coronary perfusion, especially given the patient's established CAD 2
2. Myocardial oxygen imbalance: High systolic pressure increases myocardial oxygen demand while low diastolic pressure potentially limits oxygen supply 1
3. Arterial stiffness: The wide pulse pressure reflects significant arterial stiffness, which further increases cardiac workload 3

Management Considerations

When managing this patient's blood pressure:

• Target diastolic pressure should not be excessively lowered, as values below 60 mmHg have been associated with increased coronary events in patients with CAD 4
• In patients with coronary stenosis, the autoregulatory capacity of coronary circulation is impaired, requiring higher perfusion pressures to maintain adequate flow 1
• The combination of low diastolic pressure and coronary stenosis significantly impairs coronary flow reserve 2

Pitfalls to Avoid

• Aggressive lowering of diastolic blood pressure could worsen coronary perfusion
• Focusing solely on systolic control without considering diastolic implications
• Ignoring the J-curve relationship between diastolic BP and myocardial infarction risk in high-risk patients 2

In this elderly patient with established CAD and wide pulse pressure, maintaining adequate diastolic pressure is crucial for preserving coronary perfusion while still addressing the elevated systolic pressure to reduce overall cardiovascular risk.