Cardio 2 Flashcards
Define heart block
- Atrioventricular (AV) block is a cardiac electrical disorder defined as impaired (delayed or absent) conduction from the atria to the ventricles.
- The severity of the conduction abnormality is described in degrees: first-degree; second-degree, type I (Wenckebach or Mobitz I) or type II (Mobitz II); and third-degree (complete) AV block.
Describe epidemiology of heart block
- More prevalent in African American patients
- More common over age 50
- 3rd degree incidence is 0.04%
- More common in men
Describe aetiology of heart block
- Fibrosis and calcification of the conduction system
- CAD (including patients with a chronic disease and/or an acute coronary syndrome, right coronary artery)
- Medication such as AV-nodal blocking agents (i.e., beta-blockers, calcium-channel blockers, digitalis, adenosine), anti-arrhythmic medications such as sodium-channel blockers, and some class III agents (i.e., sotalol and amiodarone).
- High vagal tone; cardiomyopathy (e.g., hypertrophic, sarcoid, amyloid, haemochromatosis); calcification from adjacent valvular calcification; post catheter ablation for arrhythmias
- Post-surgical causes (i.e., valve repair or replacement myectomy, septal ethanol ablation); blunt cardiac injury;[10]and some indigenous medicines.
- Severe electrolyte disturbance, acidosis, or hypoxaemia may result in AV block as well as neuromuscular disorders (myotonic dystrophy, Kearns-Sayre syndrome, Erb dystrophy, peroneal muscular atrophy), myocarditis, infective endocarditis, and Lyme disease.
- AV block may be congenital as well
List risk factors for heart block
- Age-related degenerative changes in the conduction system
- Increased vagal tone
- AV-nodal blocking agents
- Chronic stable CAD
- Acute coronary syndrome
- CHF
- Hypertension
- Cardiomyopathy
- Left ventricular hypertrophy
- Recent cardiac surgery
- Acid-base or electrolyte disturbance
- Neuromuscular disorders
- Sarcoidosis
- Myocarditis
- Infective endocarditis
- Hypoxemia
- Blunt cardiac injury
- Some indigenous medicines
List symptoms of heart block
Mobitz 2 and 3rd degree only
- Fatigue
- Dyspnoea
- Chest pain, palpitations, and nausea or vomiting
List signs of heart block
- Hypertension
- Cannon A waves (3rd degree heart block, irregular large wave of the JVP)
- Hypoxaemia
Describe diagnosis of heart block
- ECG
- First degree increased PR interval
- Mobitz 1 increasing PR interval then dropping a QRS complex
- Mobitz 2 PR the same with randomly dropped QRS
- Third degree P and QRS dissociated
- Troponin may be elevated, measure potassium, calcium, pH
Describe treatment of heart block
First degree or Mobitz 1
- Monitor for development
- Discontinue AV-nodal blocking medications including beta-blockers, non-dihydropyridine calcium-channel blockers, and digitalis.
- Pacemaker if symptoms continue
Mobitz II or third degree
- Discontinue AV blocking drugs
- Give atropine
- Pacemaker insertion with or without ICD
List complications of heart block
Pacemaker insertion 2-3% risk of
- Bleeding, infection, vascular trauma, pneumothorax, cardiac tamponade, lead dislodgement, and pocket haematoma development.
- The risk of MI, stroke, and death is <1%.
- Long-term complications include pulse generator or lead malfunction and infection, requiring replacement or extraction
Describe prognosis of heart block
- First-degree AV block 2-fold increase in the probability of atrial fibrillation, a 3-fold increase in the probability of pacemaker implantation, and an increase in all-cause mortality.
- In symptomatic patients with irreversible AV block, symptoms are likely to persist or potentially worsen.
- Patients with irreversible advanced AV block (type II second-degree or third-degree) are at high risk for progression to third-degree AV block or ventricular asystole.
- Low rate of pacemaker complications
Describe prognosis of ACS and angina
- Stable angina 58% of patients free of symptoms within 1 year following lifestyle modification and medical therapy
- non-ST ACS patient mortality after 6 months 4.8%
- At 12 months, rates of adverse cardiovascular events (MI and death) 10%
- NSTEMI high risk of morbidity and death, sudden death rate 4-6 times higher than general population
- STEMI in hospital mortality 4-12% and 1 year mortality 10%
List risk factors for myocarditis
- Infection (non-HIV)
- HIV infection
- Smallpox vaccination
- Autoimmune/immune-mediated diseases
- Peripartum and postnatal periods
- Drugs and toxins
Describe diagnosis of myocarditis
- 12-lead ECG (ST and T wave abnormalities, commonly ST elevation/depression)
- CXR (bilateral pulmonary infiltrates)
- Serum CK (mildly high)
- Serum CK-MB (mildly high)
- Serum troponin (I or T - elevated)
- Serum B-type natriuretic peptide (elevated in ventricular distention)
- Two-dimensional echocardiogram (global and regional left ventricular motion abnormalities and dilatation)
- Endomyocardial biopsy (EMB - myocardial cellular infiltrated and or necrosis)
- Coronary angiography (normal)
- Cardiac MRI (early enhancement myocarditis)
Define constrictive pericarditis
- A type of chronic pericarditis (lasts more than 3 months)
- Characterized by thickening and rigidity of the pericardium, resulting in both backward and forward failure. There is a characteristic pericardial knock on auscultation, which is caused by a sudden stop in ventricular diastolic filling.
- Effusive-constrictive pericarditis (the other type of chronic pericarditis) is characterized by a thickened pericardium with an effusion; this can lead to cardiac tamponade
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Describe aetiology of constrictive pericarditis
- Idiopathic
- Infectious (most commonly viral e.g., coxsackie B virus), bacterial e.g., Staphylococcus spp., Streptococcus spp., or M. tuberculosis, fungal or toxoplasmosis)
- Myocardial infarction (Postinfarction fibrinous pericarditis within 1–3 days as an immediate reaction or dressler syndrome within weeks to months following an acute myocardial infarction)
- Postoperative (postpericardiotomy syndrome): blunt or sharp trauma to the pericardium
- Uremia (e.g., due to acute or chronic renal failure)
- Radiation
- Neoplasm (e.g., Hodgkin lymphoma)
- Autoimmune connective tissue diseases (e.g., rheumatoid arthritis, systemic lupus, scleroderma)
List risks for constrictive pericarditis
- Low if idiopathic or viral pericarditis
- Intermediate risk for autoimmune and neoplastic aetiologies
- High risk for bacterial aetiologies, especially with TB and purulent pericarditis
Describe epidemiology of constrictive pericarditis
- 9% of patients with acute pericarditis
- 0.76 cases per 1,000 person-years after acute idiopathic/viral pericarditis
- 31.7 cases per 1,000 person-years for acute tuberculous pericarditis
- 52.7 cases per 1,000 person-years for purulent pericarditis
List symptoms and signs of constrictive pericarditis
Symptoms of fluid overload (i.e., backward failure)
- Jugular vein distention
- Kussmaul sign
- Hepatic vein congestion: hepatomegaly, painful liver capsule distention, hepatojugular reflux
- Peripheral edema; or anasarca, ascites with abdominal discomfort
Symptoms of reduced cardiac output (i.e., forward failure)
- Fatigue, dyspnea on exertion
- Tachycardia
- Pericardial knock: sudden cessation of ventricular filling during early diastole that is heard best at the left sternal border
- Pulsus paradoxus: ↓ blood pressure amplitude by at least 10 mm Hg during deep inspiration
List investigations for constrictive pericarditis and their findings
- Echocardiography (increased pericardial thickness)
- CT and cardiac MRI (pericardial thickening > 2 mm, calcifications, normal cardiac silhouette)
- Chest x-ray (heart size normal or slightly increased, pericardial calcifications, clear lung fields)
- Cardiac catheterization if noninvasive methods have failed to provide a definitive diagnosi (similar pressures in the left and right atria and right ventricle at the end of diastole (e.g., “equalization of pressures”), normal pulmonary artery systolic pressure < 40 mm Hg, mean right arterial pressure > 15 mm Hg)
- Square root sign - dip-and-plateau waveform, a sudden dip in the right and left ventricular pressure in early diastole followed by a plateau during the last stage of diastole
- ECG (no conclusive findings: generalized flat/inverted T waves, low QRS voltage, possible AF)
List signs on examination associated with intermittent claudication
- Wet gangrene
- Shiny hairless skin
- Ulcers
- Non-palpable pulses
- Buergers angle (pale limb under 20 degrees with flushing when the limb is lowered due to overcompensation)
Describe investigations of peripheral vascular disease
- Doppler ultrasound
- Ankle brachial index (systolic pressure of leg divided by systolic blood pressure of the arm - less than 0.41 is grounds for immediate surgical consultation)
- HbA1c, lipid screen, u&es, digital subtraction angiogram, cardio exam and lower limb exam
List signs on examination associated with limb ischaemia
- Paralysis
- Pallor
- Perrishingly cold
- Pain
- Pulseless
- Paraesthesia
Describe aetiology of limb ischaemia
Chronic
- Atherosclerosis (intermittent claudication)
Acute
- Embolus (eg. mural thrombus, AF, TB, IV drug users, malignant)
- Thrombotic (Vircows triad - ruptured plaque with clot on it)
- Aneurysm (eg. marfans)
- Iatrogenic (eg. air embolis)
Describe vircows triad
- Hypercoagulability (blood clotting due to liver failure, polycythaemoa vera)
- Stasis (long haul flights, recent surgery)
- Endothelial trauma (bruising, crush injury, plaque rupture)