Bradycardia - Heart Blocks ========================== þ Mobitz Type II - Don't confuse with blocked PACs: irregular P rhythm - True Mobitzt II: Ps are truly regular þ Complete Heart Block Etiology - often idiopathic fibrosis - may be caused by Lyme Disease þ Paradoxical Effect of Atropine to Make Bradycardia Worse: þ Should you give atropine to bradycardic MI patients with a His Bundle or infranodal block? - "The American College of Cardiology has a web site (http://www.acc.org/publications/index.html) that, among other things, has practice guidelines for various disorders including MI. Is atropine indicated in cases of bradycardia associated with infra or intra-HIS block. NO. In fact atropine should not be used (Class III) in this circumstance as it may increase the degree of AVB by accelerating the sinus mechanism. Symptomatic sinus bradycardia, Mobitz I AVB and even complete AVB (with narrow complexes in the setting of AV nodal ischemia with inferior MI) are appropriate indications for its use. Mobitz II or greater AVB in the setting of an anterior MI is usually of infra-nodal origin and atropine should not be used. þ In inferior MI, second- or third-degree blocks are often unresponsive to atropine but will respond to aminophylline. - give 100mg/min up to 250 mg [Bertolet BD, McMurtrie EB, Hill JA, Belardinelli L Theophylline for the treatment of atrioventricular block after myocardial infarction. Ann Intern Med 1995 Oct 1;123(7):509-11 OBJECTIVE: To show that second- or third-degree atrioventricular block occurring as an early complication of acute inferior myocardial infarction is mediated by adenosine. SETTING: Cardiac care unit. DESIGN: Uncontrolled, observational, hypothesis-driven study. PATIENTS: Patients who developed clinically significant atrioventricular nodal blockade within 4 hours of admission for acute inferior myocardial infarction. INTERVENTION: Theophylline, 100 mg/min intravenously to a maximum of 250 mg. MEASUREMENTS: Continuous multilead electrocardiographic monitoring before and after administration of theophylline. RESULTS: During a 6-month period, eight men who had had acute inferior myocardial infarction developed clinically significant atrioventricular block. Three had third-degree block, and five had high-grade second-degree block. In all patients, 1:1 atrioventricular nodal conduction was restored and normal sinus rhythm reappeared within 3 minutes of the administration of theophylline. All patients remained free of arrhythmia for at least 24 hours. CONCLUSIONS: Adenosine produced by the ischemic myocardium may induce atrioventricular nodal block. In our patients, atrioventricular nodal block was resistant to conventional therapy such as atropine, but it responded to the adenosine antagonist theophylline. A reference is Goodfellow J & Walker PR. Reversal of atropine resistant AV block with iv aminophylline in the early phase of inferior wall acute myocardial infarction following treatment with streptokinase. European heart Journal 16:862-865, 19995