Ventricular Tachyarrhythmias


Risk

  • VTach/VFIB are uncommon but potentially fatal dysrhythmias requiring urgent diagnosis and management.

  • Risk increases with age owing to the higher incidence of structural and ischemic heart disease and cardiac failure.

  • Primary cause of sudden death and accounts for 75–80% of sudden cardiac death. Incidence in USA is about 300,000/y and similar in other developed nations.

  • Males at greater risk (46% vs. 34%).

  • Pts under 30 with HOCM, myocarditis, RV dysplasia, or long-QT syndrome are at higher risk for VTach/VFIB.

Perioperative Risks

  • Cardiac and vascular surgery (up to 50% incidence) does not influence late mortality if LV function is preserved.

  • Low cardiac output after CABG (requiring pressors) predicts life-threatening VTach/VFIB within 72 h postop.

  • Cardiac ischemia.

  • Uncorrected electrolyte and/or acid-base disturbances, hypoxia, hypercarbia, hypothermia.

  • Use of class 1 and 3 antiarrhythmics, sympathomimetics, QT-prolonging drugs.

  • Placement of central venous catheters.

Worry About

  • Electrolyte imbalance (particularly hypokalemia and hypomagnesemia), acid-base disturbances, hypoxia, hypotension, fluid overload, ongoing myocardial ischemia, and metabolic disturbances.

  • Use of IV epinephrine and other catecholamines/sympathomimetics.

  • Drugs that prolong QT (organophosphates, antipsychotics, tricyclics) may precipitate PVT, particularly in Brugada and other long-QT syndromes.

  • Poor cardiac function.

  • Modulation of neuroendocrine stress responses.

  • R-on-T phenomenon.

  • Chest pain, SOB, palpitations, presyncope, altered mental status.

Overview

  • VTach is caused by high-frequency electrical depolarization from a ventricular myocardial focus and is characterized by a widened QRS (>0.12 sec), high rate (>120 bpm) and variable morphology (MVT or PVT) and duration (sustained vs. nonsustained).

  • Atrioventricular dissociation may be present, where p waves may be seen with or without capture/fusion beats. This implies VTach rather than SVT with aberrant conduction.

  • MVT has a single QRS morphology and can evolve into PVT. Often reentrant etiology post-MI.

  • Torsade de pointes: Atypical PVT with beat-to-beat variation, prolonged QT, changing/twisting QRS axis around baseline.

  • VFIB: Nonperfusing broad complexes (fast, chaotic, irregular, and disorganized).

  • Ventricular ectopic beats can sometimes precede VTach.

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