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Transcript
PRACTICAL APPROACH TO SVT Graham C. Wong MD MPH Division of Cardiology Vancouver General Hospital University of British Columbia CONDUCTION SYSTEM OF THE HEART His bundle SA node Left bundle AV node Right bundle USUAL CLASSIFICATION OF THE SVTs IRREGULAR REGULAR ATRIAL FIBRILLATION SINUS TACHYCARDIA MULTIFOCAL ATRIAL TACHYCARDIA ECTOPIC ATRIAL TACHYCARDIA JUNCTIONAL TACHYCARDIA ATRIAL FLUTTER WITH 2:1 BLOCK AV NODAL REENTRY TACHYCARDIA AV REENTRY TACHYCARDIA Mechanisms of supraventricular tachycardia SINUS NODE ACCESSORY ATRIAL PACEMAKER (S) RE-RENTRY SINUS TACHYCARDIA 1. ATRIAL FLUTTER 2. ECTOPIC ATRIAL TACHYCARDIA (EAT) 3. ATRIAL FIBRILLATION 4. MULTIFOCAL ATRIAL TACHYCARDIA 5. JUNCTIONAL TACHYCARDIA 1. AV NODAL REENTRY TACHYCARDIA (AVNRT) 2. AV REENTRY TACHYCARDIA (AVRT) PRINCIPLES OF THERAPY SINUS NODE BLOCK THE SAN ACCESSORY ATRIAL PACEMAKER (S) TARGET THE ACCESSORY PACEMAKER BLOCK PROPAGATION OF THE ATRIAL ARRHYTHMIA THROUGH THE AV NODE RE-RENTRY BLOCK THE RE-ENTRY CIRCUIT Anatomy of the AV Node: Implications for therapy A A V V A A V V V A V V A A A Suprahissian region V Infrahissian region AV node TREATMENT OF SVT BASED ON MECHANISM BLOCK THE SAN BETA BLOCKER CALCIUM BLOCKER BLOCK ACCESSORY PACEMAKER CLASS I OR III ANTIARRHYTHMICS ABLATION TECHNIQUES SLOW AVN CONDUCTION BLOCK THE REENTRY CIRCUIT ANY AV NODAL BLOCKING AGENT ANY AV NODAL BLOCKING AGENT Simple approach to the Regular SVTs Is there a P wave before every QRS? YES Does the P wave look normal? YES ATRIAL FLUTTER YES SINUS TACHY NO Is the rate close to 150 BPM? NO Are there P waves after the QRS? NO AVNRT YES JUNCTIONAL TACHYCARDIA AVRT NO ECTOPIC ATRIAL TACHY LET’S GET STARTED “SLOW PATHWAY” “FAST PATHWAY” -“Slow” conduction -“Fast” recovery -Bidirectional -“Fast” conduction -“Slow” recovery -Bidirectional AV NODE Atrial fibrillation and mortality: Framingham Age 55-74 Benjamin et al. Circ 1998; 98: 946-952 Age 74-94 N=296 men & 325 women OR 1.5 OR 1.9 Functional status in atrial fibrillation: impact of disease and treatment Dorian et al. Can J Cardiol 2006; 22: 383-386 Classification of Atrial Fibrillation First detected Paroxysmal ≤7 da (Self terminating) Persistent Persistent >7da-1 yr (Not self self-terminating) terminating) Permanent Patterns of AF Lone AF – young (< 60 yr), no clinical or ECHO evidence of cardiopulmonary disease or hypertension Nonvalvular AF – no rheumatic MVD, MV repair, or prosthesis Secondary AF – in setting of AMI, peri- or post-operative, myocarditis, hyperthyroid, PE, pneumonia, etc Management NO Defibrillate DECISION TREE STABLE? YES Drugs Can you safely cardiovert acute AF? 2, 3, 4 RULE If in AF for greater than TWO days (or unknown) must anticouagulate (INR 2-3) for THREE weeks before an attempt to cardiovert and then continue coumadin for FOUR weeks afterwards if successful 60% of acute AF convert spontaneously if onset <24 hrs Medications for Acute Cardioversion Rate control Rhythm control Beta blocker Amiodarone metoprolol 5mg IV q5 minutes Rate limiting calcium blocker verapamil 5mg IV q5 minutes x 3 diltiazem 5-10mg IV and 10-15mg/hr IV drip Digoxin 150-300mg IV load and then 1-2g IV/daily Sotalol 40-80mg pO BID Propafenone 450-600mg pO x 1 dose 0.5mg IV load and then 0.25mg IV q 6-8hrs x 2 Paroxysmal AFib can revert to NSR spontaneously 30% of the time within 1 day! The Stable Patient: Rate vs Rhythm Control Redux Heart Rate Control • Believed to be associated with improved symptoms, better functional status and reduced chance of tachycardia mediated cardiomyopathy • Belief is extrapololated from epidemiological data suggesting that faster heart rates in NSR associated with increased mortality • Current guidelines (little evidence underpinning) • Resting HR <80 BPM • Exercise induced HR <110 BPM Strict control Lenient control N=303 N=311 % meeting target HR 67.0% 97.7% Total # of OP visits 684 75 Mortality (%) 6.6 5.6 Min F/U 2 years, Max F/U 3 years Primary Endpoint: CV death/CHF hospitalization/CVA/TE/Bleeding/life threatening arrhythmias Van den Berg et al. NEJM 2010 Should we leave PAF alone? Insights from CARAF Overall rate of paroxysmal or chronic AF at 5 years: 63.2% Overall rate of chronic AF at 5 years: 24.7% Kerr et al. Am Heart J. 2005; 149: 489-96 The Conventional Wisdom: AFFIRM No mortality benefit from an aggressive rhythm control strategy AFFIRM Investigators. NEJM 2002; 347: 1825-1833 Nuances of AFFIRM • Mean age of patients was 70 years of age • Majority of patients had either hypertension (51%) or CAD (26%); only 12% of patients had no history of cardiovascular disease • This population is known to have increased risk of proarrhythmia from currently available antiarrhythmic drugs (AAD) • Rhythm control strategy associated with improvement in functional status Classes of available antiarrhythmic drugs and site of action Disopyramide Class Ia Procainamide Quinidine Class Ib Class Ic Class II CLASS IV Lidocaine Mexilitine Flecainide CLASS III Propafenone eg propranolol Amiodarone Bretylium Class III Dofetilide Ibutilide Sotalol Class IV non dihydropyridine calcium channel blockers eg verapamil and diltiazem ACC/AHA/ESC 2006 guidelines. J Am Coll Cardiol 2006;48:854-906. CLASS I CLASS II CTAF: Modest effect of previously available AAD Intention to treat All patients 1 in 5 patients intolerant of amiodarone Intention to treat All patients in NSR at start of trial Roy et al. NEJM 2000; 342:913-920 ATHENA: Primary Endpoint: CV Hospitalization or Death Cumulative Incidence (%) 50 Placebo on top of standard therapy* DR 400mg bid on top of standard therapy* 40 30 20 HR=0.76 p<0.001 10 Months 0 0 6 12 18 24 30 Patients at risk: Placebo 2327 1858 1625 1072 385 3 DR2400mg2bid 2301 1963 1776 1177 403 2 * Standard therapy may have included rate control agents (beta-blockers, and/or Ca-antagonist and/or digoxin) and/or anti-thrombotic therapy (Vit. K antagonists and /or aspirin and other antiplatelets therapy) and/or other cardiovascular agents such as ACEIs/ARBs and statins. Mean follow-up 21 ±5 months. Hohnloser SH et al. N Engl J Med 2009;360:668-78. COUNTERPOINT: PALLAS Connolly et al NEJM 201 365: 2268-76 Pulmonary Vein Encircling and Ablation • Can be highly effective in selected pts: • symptomatic AF • low AF burden • Normal heart • Overall success ~70-80% Functional status in atrial fibrillation: impact of disease and treatment Dorian et al. Can J Cardiol 2006; 22: 383-386 CCS Recommendations for a Rhythm Control Strategy Gillis et al. Can J Cardiol 2011; 27: 47-59
