Cardiology: Coronary Artery Disease and Angina

Coronary Artery Disease (CAD)

• Major clinical manifestations include stable angina pectoris, unstable angina pectoris, and myocardial infarction (MI)
• Angina pectoris: Ischemia leads to clinical symptoms but no death of heart muscle cells.
• MI: Ischemia is severe and leads to clinical symptoms and death of heart muscle cells.

Angina Pectoris

• Sudden onset of chest discomfort including pressure, heaviness, burning, choking sensation, and pain.
• Typically radiates to the left chest and arm.
• Frequently precipitated by triggers such as after heavy meals, going from warm to cold environments, emotional or physical stress.
• Usually lasts for a few minutes.
• Relieved by nitrites (vasodilators).
• Can radiate to the abdomen causing "indigestion."
• ECG is typically normal, but stress ECG may show changes.
• A coronary angiogram may be used to diagnose angina pectoris.
• Prinzmetal’s angina is caused by vasospasm of coronary arteries.

Stable vs. Unstable Angina

• Stable Angina: Predictable, triggered by activity, exertion, or stress. Usually resolves quickly (5-20 minutes) when resting. Pattern remains stable for > 1 month.
• Unstable Angina: Angina occurs at rest, without a trigger, and the pattern of angina changes. Symptoms may not go away and are more severe than previous angina. Can be the first experience of angina or occur within a few weeks.
• Stable angina can convert to unstable angina.
• Unstable angina can be called "preinfarction angina."
• Unstable angina can lead to MI.

Myocardial Infarction (MI)

• Symptoms: Chest pain, discomfort, nausea, vomiting, arrhythmia, loss of consciousness, and possibly sudden death.
• Pain radiates to the left arm, jaw, back, and epigastrium (stomach area).
• Many patients have had previous angina pectoris.
• Women: frequently dyspnea, weakness, and fatigue.
• 1/3 of MIs are silent.
• Diagnosis:
  • ECG: ST-elevation MI (STEMI).
  • Cardiac Enzymes: Creatine phosphokinase MB (CK-MB) and Troponin I or T.
  • Non-ST-elevation MI (NSTEMI): ST not elevated but cardiac enzymes are elevated.

Atrial Septal Defect (ASD)

• A left-right shunt develops if the septum wall does not form properly.
• Consequences are usually not as severe as VSD.
• No symptoms before age 30.
• Eventually, right heart hypertrophy develops.
• Systolic murmur is present.
• If the foramen ovale does not close, it is called "patent foramen ovale" (PFO).
• Thrombus can go from the right heart to the left heart and cause a stroke.

Patent Ductus Arteriosus (PDA)

• In the fetus, blood from the right heart bypasses the lungs via shortcuts (foramen ovale & ductus arteriosus) to the aorta.
• After birth, the lungs unfold, and blood goes through the lungs.
• The ductus arteriosus normally closes by 15 hours after birth.
• If the duct does not close, blood moves from the aorta (higher blood pressure) into the lungs, increasing blood flow through the lungs and decreasing oxygenated blood in the aorta.
• The heart has to work much harder.
• Clinically: machine-like sound over the heart.
• Right-to-left shunts can cause cyanosis.

Tetralogy of Fallot (ToF)

• Right-to-left shunt causing cyanosis.
• Four components:
  • Pulmonary stenosis
  • Large VSD
  • Overriding aorta (large aortic valve arises from both left and right ventricle)
  • Right ventricular hypertrophy.
• Most common cyanotic heart defect (5% of congenital heart disease).
• Cyanosis manifests days to weeks after birth.
• Diagnosis: Cyanosis, failure to thrive, difficulty breathing, typical posture, clubbing of fingers and toes, protrusion of sternum.
• Squatting improves symptoms.
• Blalock-Taussig (Thomas) shunt (connecting subclavian artery to pulmonary artery).
• Surgery repairs pulmonary stenosis and VSD.

Heart Valves

• Heart valve disease is more frequent for the valves of the left heart due to higher pressures in the left ventricle.
• Aortic valve and Mitral valve are most commonly affected.
• Stenosis: Failure to open completely = outflow impaired.
• Insufficiency: Failure to close completely = reflux of blood.
• Abnormal heart sound is called a "murmur."
• Rheumatic heart disease (rheumatic fever) is a major cause in underdeveloped countries.
• Other causes: Damage to valves after MI, infections, heart dilation, mitral valve prolapse, senile calcific aortic stenosis, IV drug abuse, genetic (Marfan syndrome, Ehlers-Danlos syndrome), and drugs.

Mitral Valve Insufficiency

• Also called mitral regurgitation.
• Bad prognosis due to late detection and rapid enlargement of the left atrium and left ventricle.
• Most commonly caused by mitral prolapse.
• Other causes: Rheumatic fever, ischemic heart disease, bacterial endocarditis, Fen-Phen (fenfluramine), Marfan syndrome.
• No symptoms for years, sudden decompensation, and heart failure.
• Treatment: Urgent replacement of mitral valve.
• Systolic murmur is present.

Mitral Valve Stenosis

• Narrowing of the mitral valve.
• Early symptoms include shortness of breath, pulmonary edema, "mitral face" with cyanosis of the lips, left atrial hypertrophy, pulmonary hypertension, coughing tinged with blood, and arrhythmia of the left atrium.
• Thrombosis is possible.
• Bad prognosis.
• Mid-diastolic murmur (low rumbling) is present.

Aortic Valve Insufficiency

• "Aortic Regurgitation".
• Dilation of the aortic root, valve disease.
• Aortic valve does not completely close.
• Combined concentric and eccentric left ventricular hypertrophy.
• Typically asymptomatic for a long time.
• Elevated blood pressure can lead to "head bobs" with the heartbeat.
• Early diastolic murmur, decreasing.

Aortic Valve Stenosis

• Narrowing of the aortic valve.
• Mid-systolic murmur is present.
• Mild to moderate stenosis may not show symptoms.
• More severe stenosis shows shortness of breath, angina pectoris, syncope, chest pain, and left heart failure.

Mitral Valve Prolapse

• Most common valve disorder in the industrialized world (3% of the population).
• Usually not a significant finding and discovered by chance.
• The cause is unknown - more frequent with Marfan syndrome.
• Degenerative disorder of the mitral valve.
• Usually found by ultrasound.
• Sometimes a heart sound is present.
• Good prognosis.
• Antibiotic coverage is required for tooth extractions.
• Can lead to mitral valve insufficiency.

Rheumatic Fever

• Less frequent in developed countries due to treatment of strep throat with antibiotics.
• Significant in underdeveloped countries.
• Usually affects children 6 to 15 years of age after strep throat or scarlet fever with Group A beta hemolytic Streptococcus pyogenes.
• RF symptoms occur several weeks (2-4 weeks) after the actual strep infection.
• Rheumatic fever can involve joints, heart, skin, and brain.
• An autoimmune reaction caused by antibodies formed against Strep A that also bind to tissue in joints and the heart.
• Can be prevented by antibiotic treatment of people with group A strep.
• People who have had RF frequently have relapses after infection with Strep.

Diagnosis of Rheumatic Fever (Jones Criteria)

• Major Criteria:
• Carditis (congestive heart failure, murmur, pericarditis, dyspnea)
• Migratory polyarthritis (very painful inflammation of large joints moving from joint to joint)
• Sydenham’s chorea (rapid uncontrolled movement of hands and arms; occurs late in disease)
• Erythema marginatum (long lasting rash that starts as macules, then form rings)
• Subcutaneous nodules (Aschoff bodies, painless granulomas with a necrotic center surrounded by inflammatory cells)
• Minor Criteria:
• Fever
• Arthralgia = joint pain without swelling
• Laboratory abnormalities (enhanced ESR, leukocytosis)
• ECG abnormalities (prolonged PR interval)
• Evidence for Group A Strep infection.

Bacterial Endocarditis

• Colonization of heart valves by bacteria.
• Leads to the development of thrombi mixed with bacteria called "vegetations."
• Vegetations are very friable and easily dislodge.
• Mostly bacteria, but also fungi, rickettsia, and chlamydia.
• Subacute and acute forms.
• Acute bacterial endocarditis quickly destroys heart valve and endocardium, leading to death within days or weeks.
• Clinically: Spiking fever with no clear cause, bacteremia (Streptococci, Staphylococcus aureus, Enterococci), septic emboli, petechiae, heart murmur, and splinter hemorrhages.
• Treatment with high-dose antibiotics.

Cardiomyopathy

• "Extrinsic" cardiomyopathies have an etiology outside of the heart muscle.
• "Intrinsic" cardiomyopathies have an etiology within the heart muscle.
• Most cardiomyopathies are extrinsic (ischemia = coronary artery disease).