TAILIEUCHUNG - INTERNAL MEDICINE BOARDS - PART 3

Nguyên nhân nội tại: vô căn thoái hóa lão, thiếu máu cục bộ (thường liên quan đến bức tường thấp kém hơn), quá trình truyền nhiễm (viêm nội tâm mạc, "căn bệnh Chagas, bệnh Lyme), bệnh thâm nhập (sarcoidosis, amyloidosis, hemochromatosis), bệnh tự miễn dịch (SLE, RA, xơ cứng bì); | If left untreated Lyme disease can cause varying degrees of AV conduction block at any time in the course of the disease. CARDIOVASCULAR DISEASE Bradycardia Incidence T with age. Etiologies are as follows Intrinsic causes Idiopathic senile degeneration ischemia usually involving the inferior wall infectious processes endocarditis Chagas disease Lyme disease infiltrative diseases sarcoidosis amyloidosis hemochromatosis autoimmune disease SLE RA scleroderma iatrogenic factors heart transplant surgery inherited congenital disease myotonic muscular dystrophy conditioned heart trained athletes . Extrinsic causes Autonomic neurocardiac carotid sinus hypersensitivity situational medications P-blockers calcium channel blockers clonidine digoxin antiarrhythmics metabolic electrolyte abnormalities hypothyroidism hypothermia neurologic T ICP obstructive sleep apnea . Symptoms Patients may be asymptomatic or may present with dizziness weakness fatigue heart failure or loss of consciousness syncope . Symptoms can also be related to the underlying cause of the bradycardia. Exam Look for evidence of pulse rate and evidence of the underlying cause of bradycardia. Look for cannon A waves in cases of complete AV dissociation complete heart block . Diagnosis ECG Look for the origin of the rhythm and whether dropped beats or AV dissociation is present evidence of AV block see Table . Telemetry event monitors tilt-table testing and electrophysiologic studies can also be helpful. Treatment If the patient is unstable follow ACLS protocols. If possible treat the underlying cause . endocarditis . Medications Atropine glucagon for P-blocker overdose calcium for TABLE . ECG Findings with AV Block Type of Block ECG Findings First degree Prolonged PR interval 200 msec . Second degree type I Wenckebach Progressive prolongation of the PR interval until there is a dropped QRS. Progressive shortening of the RR interval and a constant PP interval are other signs. Second degree type II .

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