L2 (PB) - Ischemic Heart Disease

What are the 3 major determinants of myocardial oxygen demand?

Ventricular wall stress, heart rate, and contractility (inotropic state)

What happens to myocardial oxygen demand when ventricular wall stress increases?

Myocardial oxygen demand increases.

What happens to myocardial oxygen demand when heart rate increases?

Myocardial oxygen demand increases.

What happens to myocardial oxygen demand when contractility increases?

Myocardial oxygen demand increases.

What 4 factors increase ventricular tension and myocardial oxygen demand?

Increased afterload, increased heart rate, increased contractility, and increased heart size.

What is preload?

Ventricular wall tension at the end of diastole; the stretch on ventricular fibers just before contraction.

What is preload clinically approximated by?

End-diastolic volume (EDV) or end-diastolic pressure (EDP).

What is afterload?

Ventricular wall tension during contraction; the force that must be overcome for the ventricles to eject blood.

What is afterload clinically approximated by?

Systolic ventricular or arterial pressure.

What is contractility?

The strength of cardiac contraction independent of preload and afterload.

What influences contractility?

Chemical or hormonal influences, such as catecholamines.

What are the 2 major contributors to ischemia in chronic CAD?

Fixed vessel narrowing and endothelial cell dysfunction.

Why does fixed coronary vessel narrowing cause ischemia?

It limits coronary blood flow and the ability of distal vessels to compensate through vasodilation.

At approximately 70% coronary stenosis, what becomes compromised?

Maximal coronary blood flow.

At greater than approximately 90% coronary stenosis, what may become compromised?

Resting coronary blood flow.

What 3 factors determine resistance to blood flow?

Vessel length, vessel radius, and blood viscosity.

How does decreasing vessel radius affect resistance?

Decreasing vessel radius greatly increases resistance to blood flow.

How does endothelial dysfunction contribute to myocardial ischemia?

Inappropriate coronary vasoconstriction and loss of normal antithrombotic properties.

What normally happens to coronary vessels during exertion or stress?

Coronary vasodilation occurs.

What normally balances coronary vascular tone during exertion?

Nitric oxide (NO) vasodilation and alpha-adrenergic vasoconstriction.

What happens during stress when the coronary endothelium is dysfunctional?

Vasoconstriction becomes unopposed and dominates.

What are other causes of myocardial ischemia besides fixed narrowing and endothelial dysfunction?

Decreased perfusion pressure and severely decreased blood oxygen content.

What 2 conditions can decrease aortic diastolic pressure?

Hypotension and aortic valve insufficiency.

What is angina pectoris?

An uncomfortable sensation in the chest and neighboring structures produced by myocardial ischemia.

What is stable angina?

A chronic pattern of transient angina precipitated by physical activity or emotional upset and relieved by rest within a few minutes.

What commonly triggers chronic stable angina?

Physical activity or emotional stress.

What typically relieves chronic stable angina?

Rest within a few minutes.

Does stable angina cause permanent myocardial damage?

No; the ischemia is transient and does not result in permanent myocardial damage.

What ECG change is often associated with stable angina?

Temporary ST-segment depression.

What is variant (Prinzmetal) angina?

Angina caused by coronary artery spasm rather than increased myocardial oxygen demand; usually occurs at rest.

What ECG change is commonly associated with variant angina?

Transient ST-segment elevation.

What is silent ischemia?

Asymptomatic episodes of myocardial ischemia detectable by ECG or other laboratory techniques.

What is unstable angina?

Increased frequency and duration of angina occurring with less exertion or at rest.

Why is unstable angina concerning?

It has a high frequency of progression to myocardial infarction if untreated.

What is a myocardial infarction?

A region of myocardial necrosis usually caused by prolonged cessation of blood supply.

What most commonly causes myocardial infarction?

Acute thrombosis at the site of coronary atherosclerotic stenosis.

How does myocardial ischemia typically present as chest pain?

Retrosternal tightness or pressure that may radiate to the neck, jaw, left shoulder, or left arm.

How long does myocardial ischemic chest pain usually last?

A few minutes, usually less than 10 minutes.

What typically triggers and relieves myocardial ischemic chest pain?

Exertion triggers it; rest or nitroglycerin relieves it.

What ECG findings can occur with myocardial ischemia?

Transient ST depression or elevation and flattened or inverted T waves.

How does pericarditis chest pain differ from myocardial ischemia?

Sharp, pleuritic pain that varies with position and can last hours to days.

What ECG findings are associated with pericarditis?

Diffuse ST elevations and PR deviation.

How does GERD typically present as chest pain?

Retrosternal burning triggered by certain foods, worsened when supine, unaffected by exertion, and relieved by antacids.

How does peptic ulcer disease typically present?

Epigastric ache or burning after meals that is unaffected by exertion and relieved by antacids.

How does esophageal spasm typically present?

Retrosternal pain with dysphagia, often precipitated by meals and unaffected by exertion.

Can esophageal spasm be relieved by nitroglycerin?

Yes.

How does biliary colic typically present?

Constant deep right upper quadrant pain lasting hours, often triggered by fatty foods.

How does costochondral syndrome typically present?

Sternal pain worsened by chest movement with tenderness at the costochondral junctions.

What typically relieves costochondral syndrome pain?

Anti-inflammatory drugs; not nitroglycerin.

How does cervical radiculitis typically present?

Constant aching or shooting pain that may follow a dermatomal distribution and worsens with neck movement.

What ECG changes occur with subendocardial ischemia?

ST-segment depression and/or T-wave flattening or inversion.

What ECG change can severe transient transmural ischemia cause?

ST-segment elevation.

What happens to ECG abnormalities when transient myocardial ischemia resolves?

The ECG abnormalities also resolve.

What is standard exercise stress testing?

Heart rate and ECG are monitored while the patient exercises on a treadmill.

What is the purpose of exercise stress testing?

To identify evidence of myocardial ischemia during increased cardiac demand.

What other types of stress testing are listed in the PowerPoint?

Nuclear imaging studies and pharmacologic testing.

What invasive diagnostic test can visualize the coronary arteries?

Coronary angiography.

What is the basic oxygen supply-demand problem in chronic stable angina?

Myocardial oxygen demand exceeds myocardial oxygen supply, typically when increased demand occurs in the presence of fixed coronary narrowing.

What is the classic pattern of chronic stable angina?

Predictable exertional chest pressure lasting a few minutes and relieved by rest or nitroglycerin.