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Table 2 Recommended responses to detected arrhythmias, the rationale, and literature behind the rationale

From: The clinical effect of arrhythmia monitoring after myocardial infarction (BIO-GUARD|MI):study protocol for a randomized controlled trial

Arrhythmia Definition according to ICM programming Recommended investigations and treatments Rationale
First incidence or sudden progression in burden of any arrhythmia   ECG to evaluate QRS width and other intervals, ischemia, etc. Echocardiography to exclude progressive HF or valve disease. Consider coronary angiogram if symptoms exceed or cannot be explained by arrhythmia severity BIO-GUARD-MI is based on data from the CARISMA trial [7]. In that study, any arrhythmia including sinus bradycardia, AV block, AF, nonsustained VT, and sustained VT/VF was associated with an increased risk of any endpoint including re-infarction, stroke, progressive HF and death. Hence, we recommend that any patient be evaluated for progressive HF or recurrence of symptomatic ischemic heart disease
AF or atrial flutter < 5.5 h RR variability > 12.5% or detected as HVR (> 160 bpm for 8 cycles) for > 6 min, but lasting < 5.5 h total/24 h (includes bigeminy rejection) Beta blocker In a large registry-based analysis, beta blockers were associated with a better prognosis in patients with AF [30], after cardiac surgery [31] and renal disease [32]. In comparison, calcium antagonists may be equally efficient for symptom relief and rate control [33], but there is currently a paucity of knowledge for best medicinal rate control methods [34]. Based on this rationale, beta blockade is the recommended primary medication for MACE prevention and for rate control in new-onset paroxysmal AF in this population
Initiation of anticoagulation therapy according to patient profile and wishes Current consensus on device-detected AF states that anticoagulation can be considered but does not necessarily need to be initiated in high-risk patients if daily episodes last < 5.5 h/day [35]. All patients in the BIO-GUARD-MI study have a CHA2DS2-VASc score indicating a high stroke risk
AF or atrial flutter > 5.5 h RR variability > 12.5% or detected as HVR (> 160 bpm for 8 cycles) > 5.5 h total/24 h (includes bigeminy rejection) Initiate anticoagulation therapy Current guidelines recommend initiation of anticoagulation treatment if the total duration of daily episodes of AF exceeds 5.5 h/day [35].
DC cardioversion if appropriate. Plan for rhythm and/or frequency management strategy. Rhythm management strategy is encouraged unless there are contraindications to this, or the patient is unwilling. Radiofrequency ablation is preferred over drug treatment as long-term rhythm management Even though rate control is not inferior to rhythm control, there is an advantage if sinus rhythm can easily be restored [8]. In a large Cochrane-based review, there seems to be a slightly higher mortality when choosing a rhythm control [36], but this seems to be due to the use of antiarrhythmic drugs, whereas catheter ablation is consistently associated with an improved outcome in high-risk patients [37, 38]
Optimize antihypertensive treatment Antihypertensive treatment has been repeatedly shown to lower the incidence of AF [39], and controlling systolic blood pressure over time seems to be key [40].
Bradycardia < 40 bpm for ≥ 10 s If < 40 bpm and symptomatic, or < 30 bpm regardless of symptoms, patient should be evaluated for optimization of medical treatment and pacemaker therapy Even though based on sparse literature, current guidelines do not recommend pacemaker implantation in asymptomatic sinus bradycardia [41]. In the CARISMA trial, sinus bradycardia was associated with an adverse outcome, mainly due to an association with progressive HF [7]. Hence, we recommend thorough evaluation of symptoms, heart function, and coronary circulation in progressive sinus bradycardia, particularly with heart rate < 30 bpm. There are currently no randomized or larger observational trials to support management of these events
Sinus arrest Pause lasting > 3 s For asymptomatic pauses > 6 s or symptomatic pauses > 3 s, adjust medicine accordingly and evaluate for pacemaker therapy Even though such pauses are considered benign and not associated with an adverse outcome, pacemaker implantation can be considered for prevention of syncope [41]. Sinus arrest was not associated with an adverse outcome in CARISMA [7]
AV block type 2 or 3 < 40 bpm for ≥ 10 s or pause > 3 s Pacemaker implantation for high-degree AV block persisting after AV nodal slowing medications. For patients with AV block, there is class I indication for pacemaker implantation regardless of symptom/arrhythmia correlation [41]
If LVEF ≤ 40% a CRT-P is recommended in patients with an expected right ventricular pacing burden > 50% Studies have shown that biventricular pacing in patients with symptomatic HF and high ventricular pacing burden can prevent HF events compared with right ventricular pacing. The precise indications in terms of ejection fraction and pacing burden are not specified in current guidelines. For the purpose of the present study, we consider the specified cut-offs reasonable
Nonsustained VT HVR > 160 bpm for 8 cycles If LVEF ≤ 35%, EPS (MADIT-I) is recommended An EPS has been shown to identify high-risk patients with previous myocardial infarction that will benefit from an ICD because of high risk of malignant arrhythmias [42, 43]
If symptomatic after beta blocker treatment, radiofrequency ablation is recommended Multiple studies have shown that radiofrequency ablation effectively treats ventricular ectopy and tachycardia [44]. While an effect on mortality has never been proved, ablation in patients with ventricular burden > 20% may restore left ventricular function in the setting of HF [45]
Sustained VT or VF HVR > 160 bpm for 8 cycles Implantation of ICD or CRT-D. Radiofrequency ablation is preferred over drug treatment as long-term rhythm management Sustained VT > 30 s or VF gives indication for an ICD according to guidelines [42, 46]. If ECG has QRS > 150 ms or observations on the ICM indicates risk of high right ventricular pacing percentage (> 40%), a CRT-D device should be implanted [41]
  1. AF atrial fibrillation, AV atrioventricular, CRT-D cardiac resynchronization therapy defibrillator, CRT-P cardiac resynchronization therapy pacemaker, DC direct current, ECG electrocardiogram, EPS electrophysiological study, HF heart failure, HVR high ventricular rate, ICD implantable cardioverter-defibrillator, ICM implantable cardiac monitor, LVEF left ventricular ejection fraction, MACE major adverse cardiac event, RR cycle length, VF ventricular fibrillation, VT ventricular tachycardia