Sustained ventricular arrhythmias

Wood M, Stambler B, Ellenbogen K. Recent insights in programmed electrical stimulation for the management of sustained ventricular arrhythmias. Curr Opin Cardiol. Jan 1994 9(1) 3-11. 

Magnesium sulfate Sustained ventricular arrhythmias Torsades de pointes of magnesium depletion or glycoside toxicity... 

Procainamide is effective against most atrial and ventricular arrhythmias. However, many clinicians attempt to avoid long-term therapy because of the requirement for frequent dosing and the common occurrence of lupus-related effects. Procainamide is the drug of second or third choice (after lidocaine or amiodarone) in most coronary care units for the treatment of sustained ventricular arrhythmias associated with acute myocardial infarction. 

Procainamide INa (primary) and IKr (secondary) blockade Slows conduction velocity and pacemaker rate prolongs action potential duration and dissociates from INa channel with intermediate kinetics direct depressant effects on sinoatrial (SA) and atrioventricular (AV) nodes Most atrial and ventricular arrhythmias drug of second choice for most sustained ventricular arrhythmias associated with acute myocardial infarction Oral, IV, IM eliminated by hepatic metabolism to /V-acetylprocainamide (NAPA see text) and renal elimination NAPA implicated in torsade de pointes in patients with renal failure Toxicity Hypotension long-term therapy produces reversible lupus-related symptoms... 

Pye M, Quinn AC, Cobbe SM. QT interval dispersion a non-invasive marker of susceptibility to arrhythmia in patients with sustained ventricular arrhythmias Br Heart J 1994 71(6) 511-14. 

Newby KH, Thompson T, Stebbins A et al. Sustained ventricular arrhythmias in patients receiving thrombolytic therapy incidence and outcomes. The GUSTO Investigators. Circulation 1998 98 2567. 

The ALPHA results contrast results of a SCD-HeFT substudy which investigated TWA in 490 patients with LVEF <35% and class II-III HF (51). In SCD-HeFT, TWA was unable to predict SCD or sustained ventricular arrhythmias. However, in SCD-HeFT the patients had a lower LVEF, a mix of ischemic and nonischemic cardiomyopathy, and a 41% indeterminate rate compared to a 20.6% rate in ALPHA, potentially lowering the predictive value of TWA. 

Kaufman ES, Bloomfield DM, Steinman RC, et al. Indeterminate microvolt T-wave alternans tests predict high risk of death or sustained ventricular arrhythmias in patients with left ventricular dysfunction. J Am Coll Cardiol 2006 48(7) 1399-404. 

In an SCD-HeFT (Sudden Cardiac Death Heart Failure Trial) substudy of MTWA, 490 patients were enrolled at 37 sites and followed for a mean of 35 months prospectively with a composite of primary endpoint of SCD, sustained ventricular arrhythmias, or an appropriate ICD discharge. This was a sick population of heart failure patients. MTWA was positive in 37%, negative in 22%, and indeterminate in 41%. There is no significant difference in survival between the MTWA positive and negative patients in the ICD and placebo arms. Mortality did not differ significantly between groups. These data indicate that MTWA results are frequently indeterminate and their ability to predict outcomes is limited. 

Randomized trials can be divided into two types primary prevention trials, in which the ICD is prophylaxis for high-risk patients, and secondary prevention trials, in which the ICD treats sustained ventricular arrhythmias already present. The latter group was more extensively evaluated at first, although... 

To reduce the risk of inappropriate withholding of therapy, programmable features such as sudden onset, rate stability, and electrogram width are usually only available for lower rate zones. In addition, manufacturers have developed another programmed feature called sustained rate duration (19). If tachycardia persists for a programmable amount of time, the ICD will deliver therapy even if stability or sudden onset criteria have not been met. Sustained rate duration can act as a safety net, reducing the likelihood of untreated sustained ventricular arrhythmias. 

The prognostic role of the occurrence of sVAs during ajmaline challenge in patients with Brugada syndrome has never been evaluated. However, the long-term prognosis of patients who developed ajmaline-induced ventricular arrhythmias was good and no further sustained ventricular arrhythmias were reported with a mean follow-up period of 29 8 months [9]. 

Young age and previously documented sinus node dysfunctions seem more frequent in patients who develop sustained ventricular arrhythmias after an ajmaline challenge. The occurrence of ajmaline-induced sVAs in patients with Brugada syndrome may not identify the group of patients with higher risk of further arrhythmic events [9]. 

Arrhythmias can range from isolated PVC s, coupled beats, non-sustained ventricular tachyarrhythmias (NSVT), sustained ventricular tachyarrhythmias (SVT) and, ultimately, ventricular fibrillation (VF). It is generally... 

Treatment of documented ventricular arrhythmias, such as sustained ventricular tachycardia, that are judged to be life-threatening. Because of the proarrhythmic effects, use with lesser arrhythmias is generally not recommended. 

Treatment of documented ventricular arrhythmias (eg, sustained ventricular tachycardia) considered to be life-threatening. 

Treatment of documented life-threatening ventricular arrhythmias, such as sustained ventricular tachycardia. 

Proarrhythmia Mexiletine can worsen arrhythmias it is uncommon in patients with less serious arrhythmias (freguent premature beats or nonsustained ventricular tachycardia) but is of greater concern in patients with life-threatening arrhythmias, such as sustained ventricular tachycardia. 

Proarrhythmia Like other antiarrhythmic agents, sotalol can provoke new or worsened ventricular arrhythmias in some patients, including sustained ventricular tachycardia or ventricular fibrillation, with potentially fatal consequences. Because of its effect on cardiac repolarization, is the most common form of proarrhythmia associated with sotalol, occurring in approximately 4% of high-risk patients. 

Moricizine is indicated for the treatment of documented ventricular arrhythmias, particularly sustained ventricular tachycardia. Moricizine was evaluated in the CAST II clinical trial for the prevention of postinfarction ventricular premature complexes. It was ineffective and found to be proarrhythmic. Patients in the moricizine arm of the trial exhibited a greater incidence of sudden cardiac death than did controls. 

Life-threatening ventricular arrhythmias, sustained ventricular tachycardia PO Initially, 100 mg q 12h, increased by 100 mg (50 mg twice a day) every 4 days until effective dose or maximum of 400 mg/day is attained. 

Supraventricular and ventricular arrhythmias (12%), nonsustained ventricular tachycardia (2%), and sustained ventricular tachycardia (1%) may occur. 

Documented, life-threatening ventricular arrhythmias, such as sustained ventricular tachycardia PO Initially, 150 mg q8h may increase at 3-to 4-day intervals to 225 mg q8h, then to 300 mg q8h. Maximum 900 mg/day PO (Extended-Release) Initially, 225mgql2h, May increase at 5-day intervals. Maximum 425 mg ql2h. 

Side effects include ventricular arrhythmias, sustained ventricular tachycardia, angina, ventricular fibrillation, headache and hypokalemia. 

These are class IC drugs with similar pharmacological profiles and with the same indication range and adverse effects. They are mainly used for the treatment of severe, lifethreatening ventricular tachyarrhythmias, and non-sustained ventricular tachycardia or high-frequency premature ventricular beats. The main adverse effects are cardiovascular, including proarrhythmic actions and severe negative inotropic effects, especially in patients with impaired cardiac function. Both flecainide and encainide increase the risk of sudden death in patients with myocardial infarction and asymptomatic unsustained ventricular arrhythmias. 

Supraventricular tachycardia is the major arrhythmia indication for verapamil. Adenosine or verapamil are preferred over older treatments (propranolol, digoxin, edrophonium, vasoconstrictor agents, and cardioversion) for termination. Verapamil can also reduce the ventricular rate in atrial fibrillation and flutter. It only rarely converts atrial flutter and fibrillation to sinus rhythm. Verapamil is occasionally useful in ventricular arrhythmias. However, intravenous verapamil in a patient with sustained ventricular tachycardia can cause hemodynamic collapse. 

Adverse reactions are similar to those of flecainide and are commoner in poor metabolisers. In addition, conduction block may occur, cardiac failure may worsen and ventricular arrhythmias may be exacerbated, and it should not be used in patients with sustained ventricular tachycardia and poor left ventricular fimction. 

Direct current (DC) electric shock applied externally is often the best way to convert cardiac arrhythmias to sinus rhythm. Many atrial or ventricular arrhythmias start as a result of transiently operating factors but, once they have begun, the abnormal mechanisms are self-sustaining. When a successful electric shock is given, the heart is depolarised, the... 

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