Cardiac Flashcards
Stable Angina
Chest pain that arises with exertion or emotional stress.
Atherosclerosis of coronary arteries >70% stenosis leads to decreased blood flow that cannot meet metabolic demand of myocaridum during exertion.
Reversible injury to myocytes
Presents with chest pain (<20mins) that radiates to L arm or jaw, diaphoresis, and SOB
ST segment depression due to subendocardial ischemia
Relieved with Nitro or rest
Unstable Angina
Chest pain that occurs at rest usually due to rupture of an atherosclerotic plaque with thrombosis (clot formation) that results in INCOMPLETE occlusion of coronary artery
Reversible injury to myocytes
ST segment depression
Relieved by Nitro
High risk of progression to MI since clot can grow to occlude entire artery
Prinzmetal Angina
Episodic chest pain not associated with exercise and due to coronary artery vasospasm
Reversible injury to myocytes
ST segment elevation due to transmural ischemia (entire wall is denied O2)
Relieved by nitro or calcium channel blockers (relieve vasospasm)
Nitroglycerin
Vasodilates arteries and veins
Main mechanism is that venodilation leads to decreased venous return to heart, leads to decreased preload, so decreased stress on the myocardium
Myocardial Infarction: Mechanisms and Clinical Presentation
Necrosis of cardiac myocytes (irreversible)
Usually due to rupture of an atherosclerotic plaque with thrombosis and COMPLETE occlusion of coronary artery. Can also be caused by coronary vasospasm (persistent prinzmental angina or cocaine use), emboli, and vasculitis (kawasaki disease in children)
Clinically appears with severe, crushing chest pain (>20mins) that radiates to L arm or jaw, diaphoresis, and dyspnea
NOT relieved by Nitro or rest
Occlusion of Left Anterior Descending
Infarction of anterior wall and anterior septum of Left Ventricle
Most common
Occlusion of Right Coronary Artery
Infarction of posterior wall, posterior septum, and papillary muscles of the left ventricle
2nd most common
Occlusion of Left Circumflex
Infarction of lateral wall of the left ventricle
Cardiac Enzymes
Troponin I = most sensitive and specific marker of MI.
Rise in 2-4hrs–>Peak at 24hrs–>Return to normal 7-10 days
CK-MB = useful for detecting reinfarction cus drops to normal quickly
Rise in 4-6hrs–>peak at 24hrs–>return to normal by 72hrs
Treatment of MI
Aspirin or Heparin = limits thrombosis
O2 = minimizes ischemia
Nitrates = vasodilate veins and arteries (mainly decreases stress on LV)
Beta blockers = slows heart rate, decreasing O2 demand and risk for arrhythmia
ACE inhibitor = decreases LV dilation by decreasing aldosterone release that decreases retention of water that would increase blood volume
Fibrinolysis or Angioplasty = opens blocked vessel
Reperfusion Injury
Reperfusion allows for:
1) Calcium influx that leads to hypercontraction of myofibrils =”contraction band necrosis”
2) O2 influx that can form free radicals and further damage myocytes and further elevate cardiac anzymes
Initial phase vs late phase of MI
1) Initially see subendocardial necrosis involving <50% of myocardial thickness and see ST segment depression
2) Continued severe ischemia leads to transmural infarction that results in ST segment elevation
<4hrs after MI
Can get cardiogenic shock, CHF, and arrhythmia if conduction system was damaged
4-24hrs after MI
dark discoloration, coagulative necrosis (removal of nucleus) and can get arrhythmia
1-3 days after MI
Yellow pallor, neutrophil infiltration, and can get fibrinous pericarditis that presents as chest pain and friction rub (only seen with trasmural infarction)
4-7 days after MI
Yellow Pallor, macrophage infiltration, and can see rupture of ventricular wall and subsequent cardiac tamponade, rupture of intraventricular septum, or papillary muscle that can lead to mitral insufficiency
1-3 weeks after MI
Red border emerges as granulation tissue enters edge of infarct and see plump fibroblasts, collagen, and blood vessels
Months after MI
White scar, fibrosis that is not as strong as original wall so can get ventricular aneurysm, mural thrombosis, dessler syndrome
Dessler Syndrome
Transmural infarction and inflammation within the pericardium which can expose pericardial antigens to immune system, can form antibodies against own pericardium and get pericarditis 6-8 weeks after MI
Sudden Cardiac Death
Unexpected death due to cardiac disease, occurs without symptoms or <1hr after symptoms arise. Usually due to ventricular arrhythmia
Usually due to acute ischemia from severe atherosclerosis
Also can be caused by mitral valve prolapse, caridomyopathy, and cocaine abuse
Chronic Ischemic Damage
Poor myocardial function due to chronic ischemic damage, progresses to CHF
Left Sided Heart Failure
Causes include ischemia, hypertension (L concentric ventricular hypertrophy leads to thick heart muscle that is hard to oxygenate and get ischemia), dilated cardiomyopathy, myocardial infarction, and restrictive cardiomyopathy.
Clinical features are pulmonary congestion that leads to pulmonary edema. See dyspnea, paroxysmal nocturnal dyspnea, orthopnea, and crackles. Small capillaries in alveoli might burst and see hemosiderin-laden macrophages.
Decreased flow to kidneys leads to activation of renin-angiotensin system that leads to fluid retention that exacerbates CHF. Therefore treatment is often ACE INHIBITORS