CH6 Ischemic Heart Disease Questions

What is ischemic heart disease?

the imbalance between myocardial oxygen supply and demand

Why does atherosclerosis cause ischemic heart disease?

the coronary arteries are narrower, decreasing blood flow and consequentially oxygen supply

What is a syndrome?

A set of symptoms or conditions that occur together and suggest the presence of a certain disease or an increased chance of developing the disease

What is angina pectoris?

chest pain due to myocardial ischemia

What is stable angina?

chronic pattern of angina pectoris caused by exercise or stress, relieved at rest.

What is variant angina?

discomfort at rest caused by coronary spasm

What is silent ischemia?

asymptomatic myocardial ischemia detected by EKG

What is unstable angina?

increased frequency and duration of angina pectoris at rest

What is myocardial infarction?

prolonged cessation of blood supply resulting from acute thrombus at coronary atherosclerotic stenosis

Oxygen supply depends on _____ and ______

oxygen content and rate of coronary blood flow (Q)

During which phase of the cardiac cycle does coronary perfusion occur?

diastole

What are the 2 components of coronary artery flow?

coronary perfusion pressure and coronary vascular resistance

Coronary artery flow is ______ to coronary perfusion pressure (P)

proportional

Coronary artery flow is ______ to coronary vascular resistance (R)

inversely proportional

Coronary perfusion pressure is approximated by -

pressure gradient between aortic diastolic pressure and LV diastolic pressure

What modulates coronary vascular resistance?

external forces that compress and internal forces that tone the coronaries

External compression occurs -

during the cardiac cycle by the contraction of the surrounding myocardium

What layer is the most vulnerable to ischemic damage?

subendocardium

What are the factors that regulate intrinsic coronary vascular resistance?

metabolic, endothelial, and neural factors

During hypoxia, the mitochondria

can't undergo oxidative phosphorylation and cannot produce ATP

What is the primary metabolic mediator of vascular tone?

Adenosine

How does adenosine cause vasodilation and increased coronary blood flow?

adenosine decreases Ca++ entry → relaxation and vasodilation → increased coronary blood flow

What are some additional metabolites that act locally as vasodilators?

lactate, acetate, hydrogen ions, and carbon dioxide

What are endothelial factors in vascular resistance?

vasoactive substances produced by the intima that change coronary tone

Nitric oxide, prostacyclin, and endothelium-derived hyper polarizing factor are _____

vasodilators

Endothelin is a ______

vasoconstrictor

Neural factors control vascular resistance through parasympathetic and sympathetic components in the ____ ____ of the adventitia

nervi vasorum

Stimulation of alpha-adrenergic receptors causes ______

vasoconstriction

Stimulation of beta2-adrenergic receptors causes ______

vasodilation

What are the 3 major determinants of myocardial O2 demand?

ventricular wall stress, heart rate, and contractility

How does high LV pressures cause wall stress?

The wall must generate an equal and opposite force to counteract the pressure and prevent rupture

Wall stress is directly related to...

LV pressure + radius

Wall stress is inversely related to...

thickness of LV wall

How does increased HR affect O2 demand?

number of contractions and ATP consumed increases → oxygen requirements rise

What effects do catecholamines and positive inotropic drugs have on contractility and O2 demand?

it increases contraction → higher oxygen requirements

What effect do negative inotropic drugs like beta-blockers have on contractility and O2 demand?

it decreases contraction → lowers oxygen requirements

The reduction in blood flow in myocardial ischemia results from a combination of -

fixed vessel narrowing and abnormal vascular tone due to endothelial dysfunction

Fluid mechanics is a physical process governed by -

Poiseuille's Law

Poiseuille's Law

Q = (π ΔP r⁴) / (8 η L)

Ohm's Law

Q = (P1-P2) / R

Resistance in a vessel

R = 8ηL / π r ⁴

How does atherosclerosis relate to resistance?

atherosclerotic plaque reduces the radius → increases resistance

Coronary arteries consist of what 2 types of segments?

large proximal vessels in epicardium and small distal resistance vessels

Which coronary artery segments are more vulnerable to atherosclerotic plaque?

proximal segments

What part of coronary arteries is usually free of plaque and can adjust their tone to meet metabolic needs?

distal vessels

Distal vessels increase their diameter during...

exertion

Distal vessels at ____ if _____

rest, proximal stenosis is severe

The severity of a coronary artery blockage depends on -

How much the proximal segments are narrowed, and how well the distal vessels dilate to compensate for the stenotic epicardial vessels

What happens with a stenosis of more than 70%?

stable angina develops with exertion

What happens with a stenosis of more than 90%?

unstable angina develops even at rest

Name the 2 ways endothelial dysfunction contributes to myocardial ischemia

Inappropriate vasoconstriction and Loss of normal antithrombotic properties

In a healthy endothelium, what causes coronary vasodilation during stress or exercise?

Increased release of nitric oxide (NO)

Why does inappropriate vasoconstriction occur in patients with atherosclerosis?

The endothelium can't release enough vasodilators to balance catecholamines

In acute coronary syndromes, plaque rupture causes platelet aggregation and clot formation. Normally, this would trigger vasodilation. What occurs with dysfunctional endothelium?

platelet-derived substances to cause more vasoconstriction, which leads to more severe ischemia

Why is platelet aggregation more likely in dysfunctional endothelium?

less NO and prostacyclin are released, so their antithrombotic effect is weakened.

During ischemia, heart cells switch from aerobic to anaerobic metabolism. How does this and reduced ATP production affect LV function?

It causes impaired contraction and relaxation, which then increases LV pressure.

How does increased LV pressure cause dyspnea?

the increased pressure backs up into pulmonary capillaries, causing pulmonary congestion and shortness of breath

What metabolic substances accumulate and why does build up of waste products cause angina?

Lactate, serotonin, or adenosine, it irritates nerve endings C7 to T4 and causes chest pain

What causes the delay in recovery of contractile function in stunned myocardium?

Calcium overload and oxygen free radicals

What causes chronic contractile dysfunction in hibernating myocardium

Persistently reduced blood flow in multivessel CAD

How is blood flow restored in hibernating myocardium?

revascularization such as PCI or CABG

What triggers stable angina, and what causes it?

predictable chest discomfort that happens with exertion or stress. It is caused by fixed atherosclerotic plaque blocking one or more coronary arteries

What is the difference between fixed-threshold angina and variable-threshold angina?

Fixed-threshold: same activity level always causes symptoms Variable-threshold: symptoms depend on changes in coronary vascular tone

What are the main ways to evaluate a patient with stable angina?

History, symptoms, physical exam, differential diagnosis, diagnostic tests, complications, and treatment

How is angina pain described?

Described as pressure, tightness, squeezing, or burning — not sharp/stabbing or affected by breathing

Why does dyspnea occur during stable angina?

LV dysfunction increases pressure → backs up into lungs → causes shortness of breath

What are the significant physical exam findings for stable angina?

increased HR and BP, mitral regurgitation murmur, dyskinetic apical impulse, S4 (stiff ventricle), carotid bruit

What causes mitral regurgitation murmur during an ischemic episode?

papillary muscle dysfunction

Name the cardiac condition that can mimic stable angina

pericarditis

Name the GI conditions that can mimic stable angina

GERD, peptic ulcer, esophageal spasm, biliary colic

Name the musculoskeletal conditions that can mimic stable angina

costochondritis, cervical radiculitis

What are the developments during a stress test that is suggestive of a significant CAD?

Happens within <3 min, Lasts >5 min post-exercise, ST depression >2 mm, Drop in systolic BP, Ventricular arrhythmias, Can't exercise >2 min

What does a stress echo help identify?

shows wall motion abnormalities before EKG changes

Why is nuclear imaging useful in patients with baseline EKG abnormalities?

Baseline EKG changes ( LBBB) can hide ischemia → nuclear imaging helps detect perfusion

In a pharmacologic stress test, how do vasodilators detect ischemia?

They dilate normal coronary arteries but not stenotic ones, causing a "steal phenomenon" — blood is diverted away from ischemic areas, revealing perfusion defects.

What is dobutamine and how does it simulate exercise?

It's a beta-1 agonist that increases heart rate and contractility, raising oxygen demand.

What is the purpose of coronary angiography?

Visualizes coronary blockages and degree of stenosis; can use FFR/iFR

What is the purpose of coronary CT angiography?

noninvasive CT imaging of coronary arteries and calcium

What are the two serious complications that stable angina can progress into?

unstable angina or myocardial infarction

What typically leads to thrombosis in coronary arteries?

Plaque rupture leads to thrombus formation

What is the first step a patient should take when experiencing stable angina?

cease exercise

How does sublingual nitroglycerin reduce myocardial oxygen demand?

causes venodilation = ↓ venous return, ↓ LV volume, ↓ wall stress = ↓ oxygen demand; also causes coronary vasodilation

How do beta-blockers reduce oxygen demand?

slow heart rate and increase diastole (more time for perfusion)

What are the treatments to prevent recurrent ischemic episodes?

beta-blockers, nitrates, calcium channel blockers, ranolazine

What are the treatments to prevent acute cardiac events?

antiplatelet therapy, lipid lowering therapy, glucose lowering therapy, ACE inhibitors

What medications prevent clot formation?

aspirin, P2Y12 inhibitors, low-dose anticoagulants

What kinds of patients benefit most from revascularization?

patients with Severe LV dysfunction, Multivessel CAD, Left main >50% stenosis, Proximal LAD disease, Diabetics

What is PTCA, and what device is commonly placed afterwards?

percutaneous transluminal coronary angioplasty uses a balloon to open blockage; stents (often drug-eluting) are placed

What vessels are most commonly used for CABG?

Internal mammary artery and great saphenous vein