Quick Recap
1. Definition
Arrhythmias are common in the cardiac surgical ICU. Beyond atrial fibrillation (cross-reference the dedicated AFib protocol), atrial flutter, ventricular tachycardia, and bradyarrhythmias/AV block each require distinct recognition and management approaches.
2. Atrial Flutter
Typical atrial flutter is a macro-re-entrant circuit involving the tricuspid annulus, with atrial depolarization at ~300/min; because only alternate waveforms typically conduct through the AV node, the ventricular rate is usually regular at ~150 bpm (2:1 block) or less commonly 75 bpm (4:1 block) — the characteristic ECG "saw-tooth" pattern in leads II, III, and aVF.
Treatment: similar to AF, with anticoagulation required. Synchronized DC cardioversion is the most effective method; pharmacological agents (amiodarone, sotalol) are far less effective for flutter than for AF. Class 1C drugs (flecainide, propafenone) are contraindicated — they can slow the flutter circuit rate enough that the AV node conducts every beat, paradoxically producing dangerous 1:1 conduction at 250-300 bpm.
A genuine, counterintuitive risk with overdrive pacing: atrial overdrive pacing can occasionally terminate flutter, but may cause it to degenerate into AF instead — not a clean fix.
For refractory, hemodynamically significant flutter: percutaneous radiofrequency catheter ablation at the cavotricuspid isthmus has a success rate over 90% with a complication rate under 1% — now a routine, first-line approach for many patients in the non-acute setting, worth considering even from the ICU for a refractory case.
3. Ventricular Tachycardia — Monomorphic vs. Polymorphic
Definition: broad complex rhythm (QRS ≥120ms) at ≥120 bpm, sustained if lasting >30 seconds. Increases myocardial oxygen demand and can degenerate into VF.
Polymorphic VT
- Beat-to-beat variation in QRS axis; causes include ischemia (graft occlusion, incomplete revascularization) or extreme electrolyte imbalance
- Torsades de pointes (polymorphic VT specifically associated with QT prolongation): from ischemia, electrolyte imbalance, or — more often — the proarrhythmic effect of drugs (antiarrhythmics, but also antibiotics and antidepressants, via potassium channel inhibition) — a genuinely broad differential extending well beyond cardiac drugs alone
- Sustained polymorphic VT requires immediate defibrillation; nonsustained episodes are managed by identifying and withdrawing/correcting the causative factor
- If ischemia is suspected, urgent coronary/graft angiography should be considered — a real, vivid example from the source text: a patient 2 days post-CABG with nonsustained polymorphic VT and ST elevation on the resting ECG was found on angiography to have an occluded right coronary graft
- IV magnesium may help in the acute setting; if bradycardia-dependent, pacing the right ventricle (epicardial wires or transvenous) can be antiarrhythmic
Monomorphic VT
- Usually arises in the setting of existing myocardial scar (previous infarction), initiated by trigger beats (ventricular ectopics, common post-cardiac-surgery); in patients with prior MI and impaired LV function, postoperative VT incidence is 30%
- Treatment: prompt electrical cardioversion for hemodynamic compromise; correct electrolyte/metabolic abnormalities; consider coronary/graft angiography if ischemia suspected
- Drug therapy: cardioselective beta-blockers can help for ischemic VT, but amiodarone is now first-line — given through a large vein, often at higher doses than used for atrial arrhythmias (5-10g loading, then 1.2g/day)
- Lidocaine works faster than amiodarone for acute termination, but has significant negative inotropic effects and is contraindicated with impaired cardiac function
- Class IC drugs (flecainide) are absolutely contraindicated in VT with ischemic heart disease; class IA drugs (procainamide) are a reasonable option if beta-blockers/amiodarone fail
- Temporary ventricular pacing can prevent bradycardia-dependent VT or terminate recurrent sustained VT via overdrive pacing
- For VT refractory to antiarrhythmic drugs: percutaneous radiofrequency catheter ablation has >75% success, though attempting this for hemodynamically stable, well-tolerated VT still carries a genuine 5% risk of serious complication (tamponade, stroke) — not a trivial intervention
ICDs — No Acute Role, But a Real Long-Term One
ICDs have no role in the acute management of VT after cardiac surgery. However, new-onset postoperative VT can recur in up to 35% of patients within the first year — in this specific cohort (particularly those with significantly impaired LV function), ICDs are substantially more effective than antiarrhythmic drugs at preventing late sudden cardiac death. Don't dismiss postoperative VT as a one-time perioperative event without considering long-term ICD referral for the appropriate patient.
Differentiating VT from SVT with Aberrancy
When in doubt, the default diagnosis is VT — findings favoring VT include AV dissociation, fusion/capture beats, extreme axis deviation, QRS duration >150ms, and precordial concordance; findings favoring SVT with bundle branch block include marked rate irregularity, QRS morphology identical to a known baseline, and termination with adenosine.
4. Bradyarrhythmias — A Genuinely Underappreciated Late Risk
All cardiac surgery patients should be considered at risk of bradycardia in the early postoperative period — either from surgical trauma to the conduction system, or unmasking of preexisting subclinical conduction disease.
Sinoatrial Disease
Manifests as sinus bradycardia, sinoatrial exit block, or sinus arrest (can predispose to junctional escape rhythms or tachycardia). Surgery involving the right atrium (e.g., ASD repair) carries the highest risk.
AV Block
- First-degree: prolonged PR, not clinically significant
- Second-degree: occasional failure of AV conduction
- Third-degree (complete): total AV conduction block, at the AV node or more distal His-Purkinje system
- Valve surgery and congenital heart defect repair carry the highest risk
- The characteristic post-CABG conduction pattern: bifascicular block (right bundle branch + left anterior fascicle) — these structures are closely approximated after division of the His bundle and share the same blood supply, so are often damaged together, producing RBBB with leftward axis on ECG
The Critical Pacing Wire Management Decision
Epicardial temporary pacing wires are routine at surgery, providing a means to increase heart rate if needed; if not present, temporary transvenous pacing is the alternative.
The permanent pacemaker decision is genuinely difficult because postoperative AV block is often transient: guidelines recommend waiting up to 2 weeks postoperatively, and nearly all patients who will regain normal AV conduction do so within 9 days. However, a real risk of "late" AV block persists even in patients who initially recover — with potentially catastrophic consequences if unmonitored. Because permanent pacemaker implantation carries a low complication rate, this protocol supports a low threshold for implantation in patients with transient complete AV block after cardiac surgery, rather than assuming initial recovery definitively excludes future risk.
Practical bedside habit: check pacing thresholds and wire function daily (cross-reference Management After Heart Transplant, this section, for the identical daily-threshold-check principle in that population) — an easily-overlooked routine task with real consequences if a wire fails silently.
5. Optimizing Heart Rate as Hemodynamic Support
A postoperative HR of 80-100 bpm is generally regarded as optimal for cardiac output. Beyond simply treating bradycardia as an arrhythmia, increasing HR in a bradycardic patient directly improves cardiac output and, by decreasing diastolic filling time and end-diastolic volume, reduces LV wall tension and improves subendocardial perfusion — a genuine hemodynamic rationale for pacing beyond just correcting an abnormal rhythm. Atrial or dual-chamber pacing is preferred over ventricular-only pacing specifically because it preserves the atrial contribution to cardiac output. If pacing isn't an option, isoprenaline (a beta-2 agonist) is a reasonable chronotropic alternative, though it can cause peripheral vasodilation and hypotension (usually fluid-responsive) as a side effect — with a bonus of pulmonary vasodilation that can offload the RV.
6. Consultation Matrix
Trigger | Consult | Timing |
Sustained VT/polymorphic VT with hemodynamic compromise | Cardiology, cardiac surgery, immediate defibrillation | Immediate |
Suspected ischemic VT | Cardiology for urgent angiography | Urgent |
Persistent/recurrent VT after initial control | Electrophysiology for ablation/ICD evaluation | Within days |
Complete AV block persisting or recurring after initial recovery | Cardiology/electrophysiology for permanent pacemaker evaluation | As identified, with low threshold |
7. Documentation & Medicolegal Checklist
- Pacing wire function and thresholds checked and documented daily
- Rationale for permanent pacemaker timing decision documented, particularly if deviating from the 2-week observation window
- VT episode characteristics (morphology, duration, hemodynamic effect, suspected cause) documented
8. Key Guidelines
- Dunning J, Treasure T, Versteegh M, et al; EACTS Audit and Guidelines Committee. Guidelines on the prevention and management of de novo atrial fibrillation after cardiac and thoracic surgery. Eur J Cardiothorac Surg. 2006;30:852-872 (also addresses broader postoperative arrhythmia principles)
9. Landmark Evidence
Finding | Data |
Cavotricuspid isthmus ablation for flutter | >90% success, <1% complication rate |
VT ablation for refractory cases | >75% success; 5% serious complication risk even for stable VT |
Postoperative VT recurrence | Up to 35% within first year; ICD more effective than drugs for late SCD prevention in impaired-LV patients |
AV block recovery timing | Nearly all recoverable cases resolve within 9 days; guideline observation window up to 2 weeks |
VT incidence with prior MI + impaired LV function | 30% postoperative VT incidence in this specific subgroup |
10. Controversies
- The permanent pacemaker timing decision for transient AV block remains genuinely difficult — this protocol favors a low implantation threshold given pacemaker's low complication rate weighed against the real risk of catastrophic late AV block, but this represents a judgment call rather than a sharply evidence-defined rule.
- Overdrive pacing for atrial flutter carries a genuine risk of precipitating AF instead — not a clean, side-effect-free alternative to cardioversion.
11. References
- Ring L, Fynn S. Rhythms. In: Klein AA, Vuylsteke A, Nashef SAM, eds. Core Topics in Cardiothoracic Critical Care. Cambridge: Cambridge University Press; 2008:137-145.
- Broomhead C. Basic haemodynamic support. In: Klein AA, Vuylsteke A, Nashef SAM, eds. Core Topics in Cardiothoracic Critical Care. Cambridge: Cambridge University Press; 2008:146-153.
- Dunning J, Treasure T, Versteegh M, et al. Guidelines on the prevention and management of de novo atrial fibrillation after cardiac and thoracic surgery. Eur J Cardiothorac Surg. 2006;30:852-872.
See also: Postoperative Atrial Fibrillation Prophylaxis After Cardiac Surgery (Cardiovascular System) for the AFib-specific evidence base; Management After Heart Transplant (this section) for the parallel daily-pacing-threshold-check principle; Bedside Resternotomy & Tamponade in the Cardiac Surgery ICU (this section) for the acute arrest-management protocol when arrhythmia causes arrest; Arrhythmias (Cardiovascular System, general population) for the non-cardiac-surgery-specific framework.