Ventricular Tachycardia in Valvular Heart Disease
ABSTRACT & COMMENTARY
Synopsis: SMVT due to BBR is common in patients after valve surgery and should be considered in the differential diagnosis of valvular heart disease patients who present with a sustained ventricular arrhythmia.
Source: Narasimhan C, et al. Circulation 1997;96: 4307-4313.
In this report, narasimhan and colleagues present data from a large, retrospective series of patients who underwent electrophysiologic study for documented or suspected ventricular arrhythmias after valve replacement or repair. Among the initial group of 96 patients, 49 patients had no inducible ventricular tachycardia (VT), eight had only polymorphic VT or ventricular fibrillation, eight had only nonsustained VT, and 31 patients had inducible sustained monomorphic VT (SMVT) during programmed ventricular stimulation. These latter patients form the subject matter for this report.The patients with inducible SMVT were divided into three groups: nine patients (group I) had VT due to bundle branch reentry (BBR), 20 patients (group II) had VT due to intramyocardial reentry, and two patients (group III) had VT due to both mechanisms. When group I and group II patients were compared, several striking differences were observed. Patients with BBR had a lower prevalence of coronary artery disease (22% vs 75%), more prolonged HV intervals (82 ± 13 vs 51 ± 15) and more frequently developed their VT in the fist month after operation (89% vs 15%). Both groups had a similar distribution of valvular lesion types, with aortic stenosis, aortic insufficiency, mitral insufficiency, and combined aortic and mitral disease seen with approximately equal frequencies. No patient in either group had mitral stenosis as their primary lesion. Induced VT due to BBR could have either a left bundle branch block morphology or a right bundle branch block morphology, but the only two clinical episodes documented electrocardiographically had a left bundle branch block pattern. However, the tachycardias were rapid and hemodynamically unstable, and some of the patients presented clinically with either syncope or cardiac arrest.
Eight of nine patients with BBR underwent radiofrequency ablation of the right bundle. All eight remained free of recurrent VT during follow-up, but two died later with congestive heart failure. Nineteen of 20 patients with myocardial VT were treated with implantable cardioverter defibrillators (ICDs). Six of these patients died due to congestive failure, one died with a nonfunctional ICD, and 10 received appropriate ICD discharges. Narasimhan et al conclude that SMVT due to BBR is common in patients after valve surgery and should be considered in the differential diagnosis of valvular heart disease patients who present with a sustained ventricular arrhythmia. Radiofrequency ablation offers a potential cure for these patients.
COMMENT BY JOHN P. DiMARCO, MD, PhD
SMVT is infrequently seen in patients with valvular heart disease. In the absence of concomitant coronary artery disease, ventricular hypertrophy, as opposed to ischemic scar, is commonly the pathologic substrate for arrhythmia. For this reason, polymorphic VT and ventricular fibrillation are the arrhythmias most commonly seen. The one exception to this principle is when valvular disease or its surgical treatment results in damage to the His-Purkinje system. Diffuse injury without production of complete block forms the substrate for BBR and can result in clinical arrhythmias.For several reasons, it is critical to make the correct diagnosis when BBR is the mechanism of sustained arrhythmia. Since the tachycardia circuit involves discrete structures that can be treated with a focal ablation procedure, this tachycardia is one of the few ventricular arrhythmias that can be readily and completely eliminated. Some patients may require permanent pacing, but others may not. These tachycardias are frequently rapid and may result in hemodynamic collapse, which, if seen in intramyocardial VT, make mapping and ablation impossible. However, once the diagnosis of BBR is made, mapping of the appropriate ablation site can be performed during sinus rhythm.
Recent data from several clinical trials have demonstrated that an ICD is superior to drug therapy as first choice therapy in patients with life-threatening arrhythmia. This trend toward early ICD implant has made the value of a baseline electrophysiologic study open to debate. At the University of Virginia, we still usually perform a baseline study to confirm the diagnosis and to identify any other potential electrophysiologic abnormalities. When the diagnosis is not in question, the baseline study often is not critical for effective initial management of patients with prior myocardial infarction. In patients with either dilated or hypertrophic cardiomyopathy or valvular disease, we still feel the baseline study should be mandatory if a monomorphic tachycardia is suspected. BBR is relatively more common in patients with these diagnoses, and the finding of VT due to BBR provides a key to a simple and highly effective treatment strategy—ablation of one of the bundle branches.
Ventricular tachycardia after cardiac valve surgery is usually due to:
a. concomitant coronary artery disease.
b. torsades de pointes.
c. bundle branch re-entry.
d. right ventricular damage.
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