Is hypertension a risk factor for myocardial infarction in adults over 40?

Is Blood Pressure a Risk Factor for Heart Attack?

Yes, hypertension is unequivocally a major risk factor for myocardial infarction in adults over 40, with the relationship between elevated blood pressure and heart attack risk being both graded and continuous starting from levels as low as 115/75 mmHg.

The Evidence for Blood Pressure as a Risk Factor

The 2017 ACC/AHA Hypertension Guidelines establish that higher systolic and diastolic blood pressure demonstrate graded, log-linear associations with increased cardiovascular disease risk, including myocardial infarction. 1 Specifically:

• A 20 mmHg increase in systolic blood pressure or a 10 mmHg increase in diastolic blood pressure is each associated with a doubling of the risk of death from stroke, heart disease, or other vascular disease 1

• In a study of over 1 million adults ≥30 years of age, higher blood pressure was directly associated with increased risk of myocardial infarction, angina, heart failure, stroke, peripheral artery disease, and abdominal aortic aneurysm 1

• This increased risk spans across all age groups from 30 to over 80 years, though the absolute risk increase is larger in older adults (≥65 years) due to their baseline higher cardiovascular risk 1

Magnitude of the Problem

Hypertension represents the leading modifiable cardiovascular risk factor for death in the United States, second only to cigarette smoking as a preventable cause of death from any cause. 1

• In 2010, high blood pressure was the leading cause of death and disability-adjusted life years worldwide 1

• More than 50% of deaths from coronary heart disease and stroke occur among individuals with hypertension 1

• In the population-based ARIC study, 25% of all cardiovascular events (including myocardial infarction and coronary revascularization) were attributable to hypertension 1

Mechanisms Linking Hypertension to Myocardial Infarction

The pathophysiologic connections are multiple and well-established:

• Left ventricular hypertrophy (LVH) is the principal mechanism by which hypertension predisposes to sudden cardiac death and myocardial infarction, with electrocardiographic LVH conferring risk comparable to coronary artery disease itself 1

• Each 50 g/m² increment in left ventricular mass increases the hazard ratio for sudden cardiac death by 1.45 (95% CI 1.10-1.92) after adjusting for other risk factors 1

• Hypertension induces endothelial dysfunction, exacerbates atherosclerosis, and contributes to atherosclerotic plaque instability 2

• LVH decreases coronary reserve and increases myocardial oxygen demand, both contributing to myocardial ischemia 2

Clinical Implications in Patients with Myocardial Infarction

A history of hypertension is highly prevalent among patients presenting with myocardial infarction and is associated with worse outcomes. 3, 4

• Hypertensive patients who suffer myocardial infarction have greater complications and mortality compared to normotensive patients 2

• Hypertension in MI patients frequently associates with female sex, diabetes, older age, and more vascular comorbidities 4

• Antecedent hypertension associates with higher rates of death and morbid events during both early and long-term follow-up after MI, particularly when complicated by left ventricular dysfunction or heart failure 4

Treatment Benefits

Blood pressure reduction through treatment significantly reduces myocardial infarction risk:

• Meta-analysis of randomized controlled trials in middle-aged subjects with diastolic hypertension showed a 14% risk reduction (95% CI 4-22%, p<0.01) in coronary death or non-fatal myocardial infarction 1

• In elderly patients with isolated systolic hypertension, treatment reduced myocardial infarction (including sudden cardiac death) by 25% 1

• Among treated hypertensive patients, achieving normotensive blood pressure levels could prevent more than 15% of myocardial infarctions 5

Important Caveats

While elevated blood pressure increases MI risk, excessively low diastolic blood pressure in treated patients may paradoxically increase coronary risk:

• A J-shaped relationship exists between treated diastolic blood pressure and myocardial infarction risk, with the lowest risk occurring at 84 mmHg 6

• At diastolic pressures of 60 mmHg, the relative risk of MI was 2.07 (95% CI 0.86-5.01), suggesting excessive lowering may compromise coronary perfusion 6

• The optimal target range for diastolic blood pressure in treated hypertensive patients appears to be 84-90 mmHg to balance benefits and risks 6

• Systolic blood pressure, in contrast, shows a linear relationship with MI risk without evidence of a J-curve 6