Snapshot A 74-year-old male with a history of a prior MI comes to your office for palpitations and light-headedness. On exam, he has a wide pulse pressure and pronounced a waves in his internal jugular vein. An EKG is ordered. Primary Heart Block (1st Degree AV Block) Introduction conduction defect notable for increased PR interval (>0.2 seconds) all atrial impulses are conducted epidemiology mostly occurs in normal, healthy individuals causes include increased vagal tone such as in highly-conditioned athletes medications slow AVN conduction Presentation symptoms asymptomatic physical exam decreased intensity of S1 on auscultation short, soft, blowing diastolic murmur at cardiac apex Evaluation EKG increased PR interval ( > 0.2 seconds) usually an incidental finding Treatment no intervention required Prognosis, Prevention, Complications prognosis is good prevention must consider conduction-slowing drug side effects complications can progress into more serious forms of heart block depending on cause reduction in ventricular stroke volume and cardiac output pacemaker syndrome Secondary Heart Block (Mobitz Type I - Wenckebach) Introduction PR interval progressively increases until beat is dropped conduction then returns to baseline and the cycle repeats epidemiology may occur in normal, otherwise healthy individuals well-conditioned athletes individuals without structural heart defects causes include increased vagal tone medications may occur in people taking Beta-blockers, digoxin, Ca-channel blockers Presentation symptoms asymptomatic in most cases presyncope recurrent syncope lightheadedness dizziness chest pain only in setting of myocarditis physical exam regularly, irregular pulse bradycardia hypotension signs of hypoperfusion in severe cases Evaluation laboratory electrolytes, calcium and magnesium cardiac enzymes if ischemia is suspected myocarditis-related studies in setting of chest pain digoxin levels EKG shows progressively increasing PR intervals predictable, interval drop of QRS complexes Treatment stop offending medication follow-up EKGs and cardiac monitoring are appropriate Prognosis, Prevention, and Complications prognosis is good in majority of cases when the block is located entirely in the AVN prevention closely monitor pharmaceutical intake and dosages complications can progress to complete heart block when located in His-Purkinje system Secondary Heart Block (Mobitz Type II) Introduction characterized by sudden, fixed dropped beat without preceding PR prolongation PR interval fixed at > 0.2 seconds causes include primary fibrotic disease usually defect in the His-Purkinje system distal to AV node scar formation prior infarction Presentation symptoms lightheadedness dizziness syncope rarely asymptomatic physical exam regularly irregular pulse bradycardia hypotension signs of hyperperfusion Evaluation laboratory electrolytes, calcium and Mg cardiac enzymes obtain if ischemia is suspected myocarditis-related studies indicated in setting of chest pain digoxin levels EKG sudden loss of QRS complex with stable PR intervals Treatment ventricular pacemaker even in asymptomatic patients Prognosis, Prevention, and Complications prognosis is poor increased chance of progessing to tertiary heart block Tertiary Heart Block (Complete AV Heart Block) Introduction no conduction through the atrioventicular node (aka, complete heart block) escape rhythm can occur anywhere between AVN and His-Purkinje system produces a fixed heart rate unable to compensate for exertion causes include congenital usually occurs at level of AVN often associated with SS-A (Ro) and SS-B (La) acquired medications antiarrhythmics digoxin degenerative diseases infections rheumatic diseases infiltrative processes neuromuscular disorders ischemia/infarct metabolic causes toxins Presentation symptoms most often profoundly symptomatic dyspnea on exertion syncope light-headedness fatigue severe chest pain sudden death physical exam irregular, weak pulse wide pulse pressure cannon A waves signs of CHF signs of hypoperfusion agitation or unease tachypnea pale complexion evaluation EKG no relationship between P-P interval and QRS interval Treatment permanent ventricular pacemaker frequent follow-up required temporary pacing is initially appropriate while conducting a work-up for potentially reversible causes Prognosis, Prevention, and Complications prognosis poor if left untreated excellent with permanent pacing prevention monitor medication levels in patients at increased risk complications pacemaker failure can lead to death other complications related to line and pacemaker placement