CARDIOLOGY P RACTICE Applying the new STEMI guidelines: 2. Disturbances of cardiac rhythm after ST-segment elevation

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The authors constitute the Comment: Patients with this ar- Canadian Cardiovascular Case 1 rhythmia generally do not re- Society Working Group, A 52-year-old man with hypertension and hyperlipidemia expe- quire an ICD, because the risk formed to review the new riences chest pain and summons medical help. Thirty minutes of recurrent sustained VT or American College of Car- later, in the presence of paramedics, he collapses with ventricu- VF is much lower than it is after diology / American Heart lar (VF). He is promptly defibrillated. His admission monomorphic VT.3 Association STEMI guide- lines and to adapt them for electrocardiogram (ECG) reveals anterior ST-segment elevation. Canadian practice. In this He receives intravenous fibrinolysis. Question: The patient’s meto- second of 2 articles, they prolol dose is increased from 50 describe cases illustrating to 100 mg twice daily, and his the care of patients with Question: Is this patient likely tricular (VT), the other medications, including an after STEMI. to have further episodes of VF? first beat having a short cou- angiotensin-converting-enzyme pling interval to the last sinus inhibitor, ASA, clopidogrel and a Comment: Whereas VF in the beat (Fig. 1). The VT stops statin, are continued. Echocar- first hour after myocardial in- spontaneously. diography shows moderately se- farction (MI) is relatively com- What is the clinical signifi- vere segmental left ventricular mon, the risk of subsequent VF cance of this ? How dysfunction, with akinesis in the is similar to that in patients should this patient be treated? anterior and inferior septum and with an MI of equivalent size apex and an estimated left ven- but without early VF.1 No spe- Comment: Self-terminating tricular ejection fraction of 30%. cific antiarrhythmic therapy is polymorphic VT, particularly On day 6, an exercise test with needed for such patients.2 in an “ischemic milieu,” often perfusion imaging shows no in- occurs during activity or sinus ducible arrhythmias and no re- Question: Later that day the pa- tachycardia, and usually starts versible . tient experiences recurrent chest with a premature ventricular Given the low ejection frac- discomfort along with new beat that is “closely coupled” tion, is this patient at increased ECG changes indicating is- (often for 300 milliseconds or risk of subsequent arrhythmias? chemia. Angiography reveals a less) to the last normal beat. Should he receive an ICD be- 90% proximal lesion in the left This is the ECG signature of fore discharge? anterior descending coronary an ischemia- or infarction-re- artery, which is treated with lated arrhythmia and is less Comment: Left ventricular func- angioplasty and stenting. The likely than monomorphic VT tion often improves after revascu- angiogram reveals only mild to imply a “fixed arrhythmo- larization. Decisions regarding disease in the patient’s other genic substrate” (myocardial the need for ICD insertion should . Apart from scar tissue from a previous in- be deferred until at least 40 days transient mild , the farct). The appropriate treat- after the acute event unless a sus- patient has no further compli- ment is vigorous anti-ischemic tained ventricular arrhythmia oc- cations. However, 48 hours after therapy. curs beyond the initial 48 hours. admission, while reading, he has If, on reassessment, the left ven- an episode of presyncope. ECG Question: Should this patient tricular function is found to be telemetry shows a 30-second receive an implantable car- only moderately impaired (ejec-

DOI:10.1503/cmaj.1041418 episode of polymorphic ven- dioverter defibrillator (ICD)? tion fraction > 40%), further in-

Fig. 1: Polymorphic (VT), arising from at 110 beats/min. Note the relatively short QT interval of 280 milliseconds and the short coupling interval from the last sinus beat to the first beat of VT of 300 milliseconds. These features suggest ischemia-related VT.

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© 2004 Canadian Medical Association or its licensors Canadian Cardiovascular Society Working Group algorithm P RACTICE

No spontaneous sustained VT or VF > 72 h after STEMI

Path A Path B Path C EF > 40% EF < 35% EF 35%–40%

• Optimal pharmacologic • Optimal pharmacologic therapy therapy No ICD • Assess for ischemia and • Assess for ischemia and revascularize if indicated revascularize if indicated

• After at least 40 d • After at least 40 d (preferably 12 wk) reassess (preferably 12 wk) reassess EF (quantitative) EF (quantitative) • If EF < 35%, • If EF < 40% and > 35% consider ICD and NSVT recorded, consider EPS. If VT induced, consider ICD

Fig. 2: Canadian Cardiovascular Society Working Group algorithm for the selection of patients for in- sertion of an implantable cardioverter defibrillator (ICD) after ST-segment elevation myocardial infarc- tion (STEMI). VT = ventricular tachycardia, VF = , EF = ejection fraction, NSVT = nonsustained VT. Reproduced with permission from reference 5. vestigations with respect to ar- Outcome: The patient is dis- left ventricular dysfunction (ejec- rhythmia risk, or ICD insertion, charged. Six weeks later, repeat tion fraction 41%). He has had no are not indicated3,4 (Fig. 2). echocardiography reveals mild further symptoms of arrhythmias.

revascularization or anti- Case 2 ischemic therapy. A 70-year-old man without prior has an initially unrecognized MI. Forty-eight hours later he presents with Question: Subsequent cardiac weakness. The ECG shows Q waves and ST-segment elevation catheterization shows moderate consistent with a recent inferior wall MI; this is confirmed by ele- left ventricular dysfunction vated creatine kinase and cardiac troponin levels. He is treated (ejection fraction 40%), inferior β with ASA, a -blocker, an angiotensin-converting-enzyme inhibitor akinesis and an occluded right and a statin. Apart from transient heart failure, he has no recurrent coronary artery with noncritical ischemia or other early complications. Three days later (5 days af- disease (< 50% stenosis) of the ter the presumed onset of MI), sustained monomorphic ventricular left anterior descending coro- flutter develops at a rate of 280 beats/min, degenerating to ventric- nary artery. Should this patient ular fibrillation (Fig. 3) and requiring immediate defibrillation. receive an ICD?

Comment: Substantial clinical Question: Is this patient at high hood of recurrent trial evidence indicates that in- risk of recurrence of this ar- and requires insertion of an im- sertion of an ICD is the best rhythmia? plantable cardioverter defibril- therapy in such cases. Anti- lator (ICD). In contrast to arrhythmic therapy, for exam- Comment: Sustained mono- polymorphic VT or VF at the ple with amiodarone, is sub- morphic VT in the presence of outset of arrhythmia, monomor- stantially inferior in both the a ventricular scar, regardless of phic VT is a consequence of short and long term for the pre- how quickly it degenerates to the ventricular scar from the vention of sudden cardiac arrest VF, strongly suggests the likeli- MI and cannot be prevented by and death.1,3

CMAJ • OCT. 26, 2004; 171 (9) 1043 P RACTICE

Fig. 3: Sustained, rapid VT quickly degenerating to a polymorphic, disorganized VT and then to VF. The monomorphic pattern at the outset suggests a “fixed arrhythmogenic substrate.”

Outcome: The patient under- Paul W. Armstrong of Cardiology/American Heart Associa- Department of Medicine tion Task Force on Practice Guidelines went implantation of an ICD (Writing Committee to Revise the 3 days later. University of Alberta 1999 Guidelines for the Management Edmonton, Alta. of Patients With Acute Myocardial In- farction). Circulation 2004;110:588-636. Paul Dorian Competing interests: Dr. Armstrong has re- 3. Wolpert C, Kuschyk J, Aramin N, Spehl S, Streitner F, Suselbeck T, et Department of Medicine ceived research funding from Hoffman- LaRoche, Aventis, Boehringer Ingelheim, al. Incidence and electrophysiological St. Michael’s Hospital and educational and consultant funding from characteristics of spontaneous ven- University of Toronto Hoffmann-LaRoche and Aventis. Dr. Dorian tricular tachyarrhythmias in high risk Toronto, Ont. received speaker fees from Guidant Corp., coronary patients and prophylactic Medtronic Inc., and St. Jude Medical Inc. implantation of a defibrillator. Heart Peter Bogaty 2004;90(6):667-71. Quebec Heart Institute 4. Connolly SJ, Hallstrom AP, Cappato Laval Hospital References R, Schron EB, Kuck KH, Zipes DP, et Sainte-Foy, Que. 1. Bokhari F, Newman D, Greene M, al. Meta-analysis of the implantable Korley V, Mangat I, Dorian P. Long- cardioverter defibrillator secondary Christopher E. Buller term comparison of the implantable prevention trials. AVID, CASH and Department of Medicine cardioverter defibrillator versus amio- CIDS studies. Antiarrhythmics vs Im- Division of Cardiology darone: eleven-year follow-up of a plantable Defibrillator study. Cardiac St. Paul’s Hospital subset of patients in the Canadian Im- Arrest Study Hamburg. Canadian Im- plantable Defibrillator Study (CIDS). plantable Defibrillator Study. Eur University of British Columbia Circulation 2004;110(2):112-6. Heart J 2000;21(24):2071-8. Vancouver, BC 2. Antman EM, Anbe DT, Armstrong 5. Armstrong PW, Bogaty P, Buller CE, Blair J. O’Neill PW, Bates ER, Green LA, Hand M, et Dorian P, O’Neill BJ. The 2004 Department of Medicine al. ACC/AHA guidelines for the man- ACC/AHA guidelines: a perspective and agement of patients with ST-elevation adaptation for Canada by the Canadian Dalhousie University myocardial infarction — executive sum- Cardiovascular Society Working Group. Halifax, NS mary: a report of the American College Can J Cardiol 2004;20(10):1075-9.

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