PracticeUpdate: Cardiology | Vol1 - No.2 - 2016

ARRHYTHMIAS/HEART RHYTHM DISORDERS

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MY APPROACH My approach to atrial fibrillation: rate vs rhythm control By Jason Andrade, MD W hen patients with atrial fibrillation are encoun- tered, physicians must <110% of age-predicted maximum on 24h Holter). In patients with significant LV dysfunction (LVEF <40%), I still favour targeting a HR of <80 bpm (while recognising that there are some post hoc data sug- gesting a target <100 bpm is also reasonable in this population).

Rate control In my practice, a primary strategy of rate control is pursued in patients similar to those enrolled in the land- mark “rate-vs-rhythm” clinical trials (eg, AFFIRM 1 ). In general, older patients (>70–75 years of age) with minimal symptoms attributable to persistent AF and in whom there is no evidence of AF-induced left ventricular (LV) dysfunction will be targeted with a strategy of ex- clusive ventricular rate control. In this less symptomatic population, rate control has been shown to im- prove symptoms, as well as reduce physician encounters and hospital admissions. In my practice, beta blockers are the preferred first-line agents owing to their efficacy (lower heart rates at rest and exercise) and potential survival advantage. I view non- dihydropyridine calcium channel blockers (ND-CCB; diltiazem and verapamil) as reasonable alternatives in patients with normal LV function and hypertension or bronchospastic airway disease but consider them as the second-line therapy owing to their relatively inferior efficacy (lesser reduction in heart rate on exertion). Of note, I prefer agents with once-daily dosing schedules in order to maximise drug adherence. Once rate control is initiated, I tar- get a resting heart rate (HR) of <100 bpm in patients free of LV dysfunc- tion and heart failure (or average HR <100 bpm and a maximum HR of

Rhythm control In my practice, a primary strat- egy of sinus rhythm maintenance (rhythm control) is undertaken in patients with a first episode of parox- ysmal AF or newly diagnosed persis- tent AF, those who are younger (<65 years) or severely symptomatic, those who are dependent on atrial “kick” (such as those with mitral stenosis or hypertrophic cardiomyopathy), or those with refractory symptoms despite adequate rate control. For these individuals, restoration and maintenance of sinus rhythm can alleviate symptoms and improve exercise capacity and quality of life. In these patients, the options are essentially threefold. In those with rare episodes of sustained AF (<1 per month) a “pill-in-the- pocket” approach with flecainide or propafenone is reasonable (with the first dose in a monitored set- ting). In those with more frequent episodes, I prefer the use of daily maintenance oral antiarrhythmic drug (AAD) therapy with flecainide, propafenone, or sotalol (preferred as first-line, with amiodarone reserved for those with ischemic heart dis- ease or significant LV dysfunction). Lastly, for those in whom AADs have been ineffective, are contrain- dicated, or cannot be tolerated, I ag- gressively advocate for percutaneous catheter ablation, which has been demonstrated to be unequivocally superior to medical therapy in this population in multiple randomised

HDL, estimated GFR, and QTc in- terval. Strikingly, a reduced EF was found in only 1% of participants in an echocardiographic substudy and did not enhance risk prediction. This risk model outperformed the 2013 ACC/AHA CVD Pooled Co- hort risk equations. These findings provide the first generalisable risk score to help estab- lish SCD risk in the general popula- tion. In the future, this risk score can be used to help prevent SCD in the highest-risk subgroups of the general population, who had a 5% risk of SCD over 10 years. Clinicians need to follow future information from this study, which will translate into reduc- ing SCD for their patients. controlled trials. In rare patients (such as those with a pulmonary vein tachycardia) I will pursue a “first-line” ablation approach (ie, prior to AAD use); however, this is the exception rather than the rule. Of note, I routinely undertake a “trial of cardioversion” in newly diagnosed patients with persistent AF, even in the absence of apparent symptoms. The reason being that sometimes the onset of symptoms can be insidious and patients do not recognise the impact of the AF on their quality of life until after sinus rhythm has been restored. If sinus rhythm maintenance results in a symptomatic improvement and subsequent AF recurrence results in symptomatic deterioration, then we consider this a strong justifica- tion for continued attempts at sinus rhythm maintenance with AAD or ablation. Conversely, should no clinical benefit be obtained with sinus rhythm restoration and should AF recurrence not be associated with clinical deterioration, then we transition to a strategy of ventricular rate control. Dr Andrade is Assistant Professor, Division of Cardiology, University of British Columbia, and Montreal Heart Institute, Université de Montréal, Canada

consider the following for all patients: reducing the morbid- ity and mortality associated with AF (predominantly by the prevention of thromboembo- lism, the universal importance of which cannot be understat- ed); and improving arrhythmia- related symptoms, exercise tolerance, and quality of life through the provision of rate and/or rhythm control.

In those with persistent symp- toms on exertion despite apparent adequate rate control, I obtain ob- jective symptom–rhythm correlation with a 24-hour monitor (or trans- telephonic event recorder) prior to the intensification of rate-control therapy. In those in whom I am unable to achieve rate control with mono- therapy, I initiate combination therapy with digoxin and a beta blocker, which has been shown to be more effective than combinations of digoxin and ND-CCB due to a synergistic effect on the AV node (digoxin working at resting condi- tions with high vagal tone and beta blockers working under stress con- ditions with high adrenergic tone). In those with refractory tachycardia despite combination therapy, I pursue the implantation of a per- manent single-chamber pacemaker with subsequent AV node ablation. Given the association with chronic right ventricular pacing and subse- quent heart failure, patients with significant LV dysfunction (LVEF <40%) will undergo implantation of a biventricular device prior to AV junction ablation.

Prediction model shows good to excellent discrimination in sudden cardiac death

Comment by Douglas Zipes, MD W hile an ejection fraction (EF) less than 35% identi- fies individuals at increased risk for sudden cardiac death (SCD), EF is a better predictor of total mor- tality than of arrhythmic mortality. In addition, most SCDs occur in

of SCD for the general population. There were 345 adjudicated SCD events in the analysis that found 12 independent risk factors for SCD that included age, male sex, African American race, current smoking, systolic blood pressure, use of anti- hypertensive medication, diabetes, serum potassium, serum albumin,

vast majority of the 350,000 SCD population. The purpose of this study of 13,677 individuals in the Athero- sclerosis Risk in Communities Study (ARIC) and 4207 participants in the Cardiovascular Health Study (CHS) free of baseline cardiovascular dis- ease was to derive a prediction model

the general population among indi- viduals with no past history of car- diac disease in whom the EF is not reduced. The SCD event is often the first manifestation of the presence of underlying heart disease. Therefore, predicting those at risk for SCD from the general population has been a major challenge. They represent the

Development and validation of a sudden cardiac death predictionmodel for the general population Circulation Take-home message

factors in the ARIC study included age, male sex, African American race, current smoking, systolic blood pressure, use of antihypertensive medication, diabetes, serum potassium, serum albumin, HDL, estimated GFR, and QTc interval. Over a 10-year follow-up period, a model combining these risk factors showed good to excellent discrimination for SCD risk (C statistic 0.820 in ARIC and 0.745 in CHS). The SCD prediction model was slightly better in predicting SCD than the 2013 ACC/AHA Pooled Cohort risk equations (C statistic 0.808 in ARIC and 0.743 in CHS). Only the SCD prediction model, however, dem- onstrated similar and accurate prediction for SCD using both the original, uncalibrated score and the recalibrated equation. Finally, in the echocardiographic subcohort, a left ventricular ejection fraction <50%was present in only 1.1% of participants and did not enhance SCD prediction. CONCLUSIONS Our study is the first to derive and validate a generalizable risk score that provides well- calibrated, absolute risk estimates across different risk strata in an adult population of white and African American individuals without a clinical diagnosis of cardiovascular disease. Circulation 2016 Aug 19;[Epub ahead of print], Deo R, Norby FL, Katz R, et al.

Dr Zipes is Distinguished Professor, Professor Emeritus of Medicine,

• The authors sought to develop and validate a new sudden cardiac death (SCD) prediction model for the general US population based on the Atherosclerosis Risk in Communities Study (ARIC; n=13,677) and the Cardiovascular Health Study (CHS; n=4207). Results showed that, over a 10-year follow-up period, the 12 independent risk factors identified produced a C-statistic of 0.82 in ARIC and 0.745 in the CHS studies, edging out the ACC/AHA risk equations (C-statistic of 0.808 and 0.743 for ARIC and CHS, respectively). • This new risk equation provides slightly better predictive ability for SCD than the ACC/AHA model and is generalisable to the US population without cardiovascular disease.

Pharmacology and Toxicology,

Emeritus Director of the Division of Cardiology and Krannert Institute of Cardiology, Indiana University School of Medicine in the US.

Abstract BACKGROUND Most sudden cardiac death (SCD) events occur in the general population among persons who do not have any prior history of clinical heart disease. We sought to develop a predictive model of SCD among US adults. METHODS We evaluated a series of demographic, clini- cal, laboratory, electrocardiographic, and echocardio- graphic measures in participants in the Atherosclerosis Risk in Communities (ARIC) Study (n=13,677) and the Cardiovascular Health Study (CHS) (n=4207) who were

free of baseline cardiovascular disease. Our initial ob- jective was to derive a SCD prediction model using the ARIC cohort and validate it in CHS. Independent risk factors for SCD were first identified in the ARIC cohort to derive a 10-year risk model of SCD. We compared the prediction of SCD to non-SCD and all-cause mortal- ity in both the derivation and validation cohorts. Further, we evaluated whether the SCD prediction equation was better at predicting SCD than the 2013 ACC/AHA CVD Pooled Cohort risk equation. RESULTS There were a total of 345 adjudicated SCD events in our analyses, and the 12 independent risk

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VOL. 1 • No. 2 • 2016