ECG effects of antiarrhythmics

RED FLAG Use class II antiarrhythmics cautiously in patients with pulmonary disease. 

Exerts direct effects on electrical properties of the heart. 

A pacemaker is a device that stimulates the myocardium to depolarize by generating electrical impulses and conducting them to the heart. 

Typically, a pacemaker may be needed after a myocardial infarction (Ml) or cardiac surgery. Pacemakers are commonly used to treat irreversible heart conduction problems, and they may be used for other indications as well  

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Verapamil (Class IV antiarrhythmic drug) is an effective agent for atrial or supraventricular tachycardia. A Ca++ channel blocker, it is most potent in tissues where the action potentials depend on calcium currents, including slow-response tissues such as the SA node and the AV node. The effects of verapamil include a decrease in heart rate and in conduction velocity of the electrical impulse through the AV node. The resulting increase in duration of the AV nodal delay, which is illustrated by a lengthening of the PR segment in the ECG, reduces the number of impulses permitted to penetrate to the ventricles to cause contraction. 

Un, acute exacerbation of chronic bronchitis prophylaxis in transurethral procedures Action Quinolone antibiotic -1- DNA gyrase. Dose 400 mg/d PO X w/ renal insuff, avoid antacids Caution [C, —] Interactions w/ cation-containing products Contra Quinolone all gy, children <18 y,T QT interval, X Disp Tabs SE NA/ /D, abd pain, photosens, Szs, HA, dizziness, tendon rupture, periph al neuropathy, pseudomembranous cohtis, anaphylaxis Interactions t Effects W/ cimetidine, probenecid T effects OF cyclosporine, warfarin, caffeine X effects W/ antacids EMS Monitor ECG for TqT int val, esp in pts taking class lA/III antiarrhythmics monitor ECG and BP for signs of h5 povolemia and electrol5rte disturbances (hypokalemia) d/t D T risk of photosensitivity Rxns OD May cause NA /D, confusion and Szs symptomatic and supportive... 

Procainamide (Pronestyl, Pronestyl SR, Procanbid) [Antiarrhythmic] WARNING Only use in life-treating arrhythmias hematologic tox can be severe Uses Supraventricular/ventricular arrhythmias Action Class 1A antiarrhythmic (Table VI-7) Dose Adults. Recurrent VF/pulseless VT 20 mg/min slow IV inf to a max of 17 mg/kg or until QRS T by 50% or dysrhythmia resolves Maint inf 4 mg/min (mix 1 gm in 250 mL NS to make 4 mg/mL use 60 gtt set—60 gtt/min = 4 mg) Peds. Loading dose 15-50 mg/kg IV/IO Caution [C, +] Contra Complete heart block, 2nd- or 3rd-degree heart block w/o pacemaker, torsades de pointes, SLE Disp Tabs caps 250, 500 mg SR tabs 500, 750, 1000 mg inj 100, 500 mg/mL SE 1 BP, lupus-like synd, GI upset, taste perversion, arrhythmias, tach, heart block, angioneurotic edema, blood dyscrasias Interactions T Effects W/ acetazolamide, amiodarone, cimetidine, ranitidine, trimethoprim T effects OF anticholinergics, antihypertensives i effects W/ procaine, EtOH EMS Monitor BP and ECG use caution to prevent rapid... 

INHALATIONAL ANTIARRHYTHMICS -AMIODARONE Amiodarone may t myocardial depressant effects of inhalational anaesthetics Additive effect Monitor PR, BP and ECG closely... 

A patient is admitted to the emergency department for evaluation of an abnormal ECG. Overdose of an antiarrhythmic drug is considered. Which of the following drugs is correctly paired with its ECG effects ... 

Glass lA Antiarrhythmic Agents. Class lA antiarrhythmic agents decrease automaticity, ie, depress pacemaker rates, especially ectopic foci rates produce moderate depression of phase 0 depolarization and thus slow conduction in atria, A-V node, His-Purkinje system, and ventricles prolong repolarization, ie, lengthen action potential duration increase refractoriness and depress excitabiHty. These electrophysiological effects are manifested in the ECG by increases in the PR, QRS, and QT intervals. 

Glass IB Antiarrhythmic Agents. Class IB antiarrhythmic agents produce less inhibition of the inward sodium current than Class lA agents. In normal myocardial tissue, phase 0 may be unaffected or minimally depressed. However, in ischemic or infarcted tissue, phase 0 is depressed. Myocardial tissue exposed to Class IB agents exhibits decreased automaticity, shortened action potential duration, ie, shortened repolarization, and shortened refractory period. Excitability of the myocardium is not affected and conduction velocity is increased or not modified. The refractory period is shortened less than its action potential duration, thus the ratio of refractory period to action potential duration is increased by these agents. The net effect is increased refractoriness. The PR and QT intervals of the ECG are shortened and the QRS interval is unchanged (1,2). 

Glass IG Antiarrhythmic Agents. Class IC antiarrhythmic agents have marked local anesthetic effects. They slow the rapid inward sodium current producing marked phase 0 depression and slow conduction. Action potential duration of ventricular muscle is increased, ie, prolonged repolarization, but decreased in the His-Purkinie system by these agents. The effects on the ECG are increased PR interval, marked prolongation of the... 

The Class III antiarrhythmic agents markedly prolong action potential duration and effective refractory period of cardiac tissue. The QT interval of the ECG is markedly prolonged. 

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