ISCHEMIC HEART DISEASE I

Ischemic heart disease is AKA:

coronary artery disease

What is the main cause of IHD

coronary atherosclerosis

define ischemia

reduced blood flow to tissue

define hypoxemia

deficiency of oxygen in the blood

What are the typical symptoms of IHD

angina - chest pain

dyspnea - shortness of breath

diaphoresis - excessive sweating

What is the main risk factor for IHD?

coronary atherosclerosis

what percentage of IHD cases result from coronary atherosclerosis

90%

T/F: Coronary atherosclerosis is a slowly progressive, silent process that begins decades before symptoms occur.

true

What are other contributing factors to IHD?

diabetes

peripheral artery disease

chronic kidney disease

hypertension

hyperlipidemia

family history

smoking

obesity, sedentary lifestyle

IHD is responsible for what percentage of global deaths?

>12%

How many heart deaths per year occur in US?

~659,000

1/4

IHD caused how many deaths in 2019 in US?

360,900

What ratio of MIs are silent?

1 in 5 do not have symptoms or have very mild symptoms

Myocardial infarction: ~ ———-/year; _______/first time

805,000

605,000

T/F: mortality is down ~50% since 1960s with little to no potential for increase.

False. mortality is down ~50% but progress is threatened by aging and obesity epidemic

What are the four clinical syndromes of IHD?

1. Angina Pectoris

2. Myocardial Infarction

3. Chronic IHD with heart failure

4. sudden cardiac death

What are the three subtypes of angina pectoris?

stable

unstable

variant (vasospastic/prinzmetal) angina

What are the three subtypes of MI?

subendocardial

transmural

multifocal microinfarction

In stable angina, symptoms are generally absent until what occurs?

~75% occlusion with plaque

How would a patient with stable angina present?

with a stable pattern over time

stable atherosclerotic plaque

stenosis of <70% (which is why they are not presenting with symptoms)

normal biomarkers

What are the characteristics associated with stable atherosclerotic plaque?

ischemic chest pain with exertion

relieved by rest

no plaque rupture/thrombosis

What is the diagnosis for stable angina? Why?

cardiac stress test, which increases the demand for O2

How does the ischemic chest pain with unstable angina present?

ischemic chest pain longer than 20 minutes occurring at rest or with minimal exertion

What has occurred with the atherosclerotic plaque in unstable angina?

it has ruptured

T/F: There is thrombus formation with unstable angina.

true

What is the average percentage of stenosis in unstable angina?

>70%

What might the ECG show with unstable angina?

ST depressions or T wave inversions

T/F: With unstable angina, the biomarkers are also elevated.

False. normal biomarkers

What is Variant (prinzmetal) angina a subtype of?

unstable angina

What causes the ischemia with variant angina?

vasospasm, not obstruction

When does angina occur with variant angina?

at rest

Chest pain with variant angina is associated with what ECG display?

ST segment elevation

What is the biomarker status of patients with variant angina?

normal biomarkers

If variant angina spasm is prolonged, what could it progress to?

myocardial infarction

What are additional risk factors and triggers for variant angina?

cigarette smoking

cocaine

alcohol

triggers can include amphetamines, sumatriptan, marijuana

What are treatment options for variant prinzmetal angina?

quit smoking

Calcium channel blockers, nitrates

Avoid beta-blockers (propranolol)

What is the role of calcium channel blockers and nitrates in variant angina?

vasodilators that oppose spasm

Why is it important to avoid beta blockers such as propranolol in patients with variant angina?

non-selective blockers

can cause unopposed alpha-1 stimulation

symptoms may worsen

what are three main complications of atherosclerosis leading to ischemia?

1. stenosis - reduction in coronary blood flow

2. acute plaque change - plaque rupture, erosion/ulceration, hemorrhage —> thrombosis or embolization

3. aneurysm - vessel wall destruction —> thrombosis or rupture

Define a vulnerable plaque.

thin fibrous caps, large lipid cores, and greater inflammation.

if it ruptures, hemorrhage occurs leading to thrombosis and micro-embolization

Define a stable plaque.

Thickened and densely collagenous fibrous caps with minimal inflammation and underlying atheromatous core

Plaque changes result in ______ formation, causing acute coronary syndrome, which may include:

thrombosis

Unstable angina, Stable angina, MI, Sudden death

Where does the plaque rupture typically occur?

at the shoulder of the fibrous cap

What chemical factors are involved in plaque rupture?

inflammatory cells int he cap release substances that can weaken it

y-interferon (T-cells) decrease collagen synthesis

metalloproteinases degrade matrix

How do emotional and physical stressors lead to plaque rupture?

emotional stress leads to sympathetic activation

high BP, tachycardia, and strong ventricular contraction

What is the layman’s term for myocardial infarction?

heart attack

What causes myocardial infarction?

necrosis of the heart muscle from prolonged severe ischemia usually due to thrombosis triggered by a sudden change in plaque.

May be due to a rupture or fissuring, endothelial erosion or ulceration, or plaque hemorrhage

How would an ECG look for a patient with MI?

ST elevation

T inverted

What are three common coronary artery occlusion sites?

Left Anterior Descending Artery

Right Coronary Artery

Left Circumflex Artery

What percentage of coronary artery occlusion occurs at the LAD?

40-50%

What percentage of coronary artery occlusion occurs at the RCA?

30-40%

What percentage of coronary artery occlusion occurs at the LCx?

15-20%

Which occlusion site is described as the site of the infarct is anterior LV, apex circumferentially, and the anterior 2/3 of the septum?

LAD

Which occlusion site is described as the right ventricular free wall, inferior/posterior wall of LV, posterior portion of the ventricular septum?

RCA

Which occlusion site is described as the lateral wall of the left ventricle?

LCx

How does right ventricular MI present clinically?

Jugular venous distention due to occlusion in RCA & SVC leading to backflow

Edema in lower extremity

Hypotension (Decreased preload, CO, HR)

arrhythmia (sinus arrhythmia, AV block)

Right ventricular MI affects which sections of the heart?

Posterior wall of the left ventricle

posterior septum

right ventricle

Left ventricular MI affects which sections of the heart?

LAD:

• anterior wall of left ventricle

• anterior septum

LCx:

• lateral wall of left ventricle

How does left ventricular MI present clinically?

pulmonary edema due to increased pressure and backflow

hypotension

S4 sound - ventricle is stiff and makes noise

reflex tachycardia

arrhythmia - ventricular tachycardia, ventricular fibrillation

What are the patterns of subendocardial MI?

Stenosis <90%

limited to the inner myocardial layer (NSTEMI)

ECG: ST depression, T wave inversion

What are the patterns of Transmural MI?

complete occlusion (100%)

involves full myocardial wall (STEMI)

ECG: ST elevation

What are the patterns of multifocal microinfarction?

microvascular occlusion - microemboli, vasospasm, vasculitis

ECG: nonspecific changes

Which pattern of infarction is limited to the inner myocardial layer NSTEMI?

subendocardial MI

Which pattern of infarction involves the full myocardial wall STEMI?

transmural MI

Which pattern of infarction includes microvascular occlusion?

multifocal microinfarction

Which pattern of infarction is responsible for ST depression and T wave inversion?

subendocardial MI

Which pattern of infarction is responsible for ST elevation?

transmural MI

Which pattern of infarction has nonspecific ECG changes?

multifocal microinfarction

What is the term used when LAD, LCx, and RDA are each affected?

global hypotension subendocardial infarction

What is the reversible damage associated with the myocardial response to ischemia?

loss of contractility in 60 seconds

ultrastructural changes in minutes: myofibrillar relaxation, cell & mitochondrial swelling

what is the irreversible damage associated with the myocardial response to ischemia?

severe ischemia <=10% of blood flow for 20-30 minutes —> necrosis

structural defects in sarcolemma —> leakage of proteins measurable in blood

What are the classic clinical symptoms of MI?

chest pressure

crushing

squeezing

sharp/stabbing pain

dyspnea

nausea/vomiting

diaphoresis

left arm/jaw pain

What percentage of patients with MI are asymptomatic with nonspecific symptoms?

25%

What are the ECG changes seen with MI?

ST segment

T wave

Q wave alterations

Can be normal despite MI

What is the laboratory evaluation for cardiac biomarkers with MI diagnosis?

Proteins leaked from necrotic cardiomyocytes

What kind of myocyte proteins are released in myocardial infarction?

troponin I

troponin T

~ used for diagnostic biomarkers of myocyte injury

T/F: biomarkers spilling into the blood with cardiac injury is specific for MI.

false. it is not specific for MI

What may also be elevated in skeletal muscle injury?

myoglobin

After injury, what is the timeline for myoglobin elevation, peak, and return to normal?

Elevated in 30 minutes to 4 hours

Peaks at 6-7 hours

Back to normal in 24 hours

__________ is mostly found in cardiac muscle; however, still found in small amounts in skeletal muscle.

CK-MB

Creatine kinase, MB

After injury, what is the timeline for CK-MB to rise, peak, and return to normal?

Rises 3-12 hours after onset of infarction

Peak is at 24 hours

Back to normal in 2-3 days

What is the most common marker used for the laboratory evaluation of infarctions?

troponin I or T, which are cardiac specific proteins

After injury, what is the timeline for Troponin I or T to rise, peak, and return to normal?

Rises by 3-12 hours after MI

Peak is at 24 hours

Normalize within 10-14 days

Which laboratory evaluation marker for infarction is not very specific?

lactate dehydrogenase

After injury, what is the timeline for lactate dehydrogenase for elevation, peaking, and return to normal?

elevated by 8-12 hours

peaks at ~3 days

back to normal in 10-14 days

If a patient experiences an STEMI, before they get to the hospital, what should be done?

provide oxygen: the decreased blood flow reduces oxygen levels in circulation

provide an antiplatelet agent: aspirin 325 mg prevents platelet aggregation and clot formation

provide a vasodilator: nitroglycerin relaxes vessels to increase coronary perfusion, increases coronary blood flow and reduces cardiac workload

If a patient experiences an STEMI, when they arrive at the hospital with oxygen, antiplatelet agent, and the vasodilator, what should be provided next?

• pain relief - morphine

• anticoagulant - heparin

• ACE inhibitor - vasodilation, lowers angiotensin II —> reduces resistance

• Beta blocker - slows heart rate, reduces cardiac output and myocardial oxygen demand

• Calcium channel blocker - decreases contractility, relaxes vessels

• statin - lowers cholesterol (atherosclerosis)

• Coronary angiography - opens the blocked artery; balloon and stent placement

Multifocal microinfarction is also known as:

microvascular angina

Microvascular angina is also known as:

Cardiac syndrome X

Primary MVA includes the dysfunction of small _______ (100-400 um) and ______ (<100 um).

intramyocardial arteries

arterioles

Microvascular angina can coexist with:

macrovascular coronary disease

Secondary Microvascular angina can occur due to _______ causing _______.

underlying conditions

microvascular damage

What are four examples of secondary MVA?

Left ventricular hypertrophy from hypertension

systemic sclerosis - an autoimmune disease with widespread microvascular damage

systemic amyloidosis - accumulated misfolded protein obstruction within the heart

smoking

What are two clinical features of microvascular angina?

angina-like chest pain with exertion

symptoms improve with rest

Which population is at an increased risk for microvascular angina?

more common in peri- or post-menopausal women (~40y.o. mean age)

What are the three diagnostic tests for microvascular angina?

exercise stress test: ST depression

coronary angiography: normal or mild stenosis (<30%)

MRI or PET: may detect microvascular dysfunction

What are the treatment options for microvascular angina?

lifestyle change

nitroglycerin - immediate tx

calcium channel blocker - long term tx

How often can nitroglycerin be provided to a patient?

every 5 minutes up to 3x if blood pressure is stable (90 mmHg)

occlusion of which artery would most directly cause ischemia in the lateral wall of the left ventricle?

LCx

What role do beta-blockers play in treating STEMI patients in hospital?

reduce heart rate and myocardial oxygen demands