Determinants of the outcome of electrophysiologic study in patients with ventricular tachyarrhythmias.

To determine those factors predictive of the ability to both initiate and suppress ventricular tachyarrhythmias during electrophysiologic study, the results of programmed cardiac stimulation were evaluated in 261 patients: 66 presenting with nonsustained ventricular tachycardia, 91 with sustained ventricular tachycardia and 104 with ventricular fibrillation. Multivariate logistic regression analysis revealed that the presenting arrhythmia was a potent and independent predictor of the ability to provoke ventricular arrhythmias at electrophysiologic study; a history of myocardial infarction and male sex were also significant independent predictors. Of patients presenting with sustained ventricular tachycardia, 89% (81 of 91) had inducible ventricular arrhythmias compared with 61 (40 of 66) and 66% (69 of 104) of patients with nonsustained ventricular tachycardia and ventricular fibrillation, respectively. Complete suppression of inducible arrhythmias could be achieved in only 52% (34 of 66) of patients with sustained ventricular tachycardia, compared with 73 (24 of 33) and 75% (46 of 61) of patients presenting with nonsustained ventricular tachycardia and ventricular fibrillation, respectively. Multivariate analysis showed that the major independent determinants of the ability to suppress inducible arrhythmias were the number of drug trials performed before electrophysiologic study (inversely correlated) and the nature of the induced arrhythmia. The nature of the presenting clinical arrhythmia is, therefore, a highly significant and independent predictor of the ability to induce ventricular arrhythmias during electrophysiologic testing and an important determinant of the ability to suppress induced arrhythmias in patients with spontaneous ventricular tachyarrhythmias.

Underestimation of prosthetic mitral valve areas: role of transseptal catheterization in avoiding unnecessary repeat mitral valve surgery.

In patients with symptoms of heart failure after mitral valve replacement, identification of a stenosed prosthesis may be difficult. Twelve such patients were evaluated, presenting at a mean of 8.4 years after mitral valve replacement (four mechanical, eight porcine). Transvalvular pressure gradients were obtained using both indirect (pulmonary capillary wedge) and direct (transseptal catheterization) measurements of left atrial pressure. In all 12 patients, the diastolic gradient across the prosthetic valve was overestimated when pulmonary wedge rather than transseptal measurements were used. Calculated mitral valve prosthetic area was underestimated by the pulmonary wedge determinations. These findings may be caused by either the phase delay of the pulmonary wedge V wave relative to the transseptal V wave, resulting in a higher diastolic mean left atrial pressure, or the faulty wedge determinations in the setting of pulmonary hypertension, or both. In patients being considered for repeat mitral valve replacement because of prosthetic valve stenosis, transseptal catheterization allows for more accurate determination of prosthetic valve area and more accurately defines the need for repeat mitral valve surgery.

Programmed ventricular stimulation in patients with left ventricular dysfunction and ventricular tachycardia: effects of acute hemodynamic improvement due to nitroprusside.

To assess the electrophysiologic effects of acute hemodynamic improvement in patients with left ventricular systolic dysfunction, 12 patients with a left ventricular ejection fraction less than 0.40 and a history of sustained monomorphic ventricular tachycardia were studied. All patients had underlying coronary artery disease. Patients underwent programmed cardiac stimulation in random order during a baseline period and with nitroprusside infusion. Mean pulmonary capillary wedge pressure decreased from 20 +/- 8 mm Hg at baseline study to 8 +/- 3 mm Hg during nitroprusside infusion (p less than 0.0001). Pulmonary artery, right atrial and systemic arterial pressures also decreased with nitroprusside (p less than 0.01). Cardiac output did not change. Left ventricular dimensions, determined by two-dimensional echocardiography, decreased significantly during nitroprusside infusion. The right ventricular effective refractory period, measured during ventricular drive trains at cycle lengths of 400 and 600 ms, were similar during baseline and nitroprusside periods (271 +/- 30 versus 274 +/- 31 ms at 600 ms, and 249 +/- 25 versus 246 +/- 18 ms at 400 ms). In 2 patients no ventricular arrhythmias were induced during either study period; in the other 10, ventricular tachyarrhythmias were induced during both periods. The mean number of extrastimuli required to induce a ventricular tachyarrhythmia was similar during the baseline period (1.8 +/- 0.6) and during nitroprusside infusion (1.9 +/- 0.7). As well, the mean cycle length of ventricular tachycardia induced was similar during the baseline period (347 +/- 61 ms) and during nitroprusside infusion (342 +/- 70 ms).(ABSTRACT TRUNCATED AT 250 WORDS)

Usefulness of electrophysiologic studies for new-onset sustained ventricular tachyarrhythmias shortly after coronary artery bypass grafting.

We retrospectively studied a group of 17 patients who developed life-threatening ventricular tachyarrhythmias shortly after coronary artery bypass grafting. The initial clinical event was sustained monomorphic ventricular tachycardia (VT) in 15 and ventricular fibrillation (VF) in 2, occurring at an average of 3.6 days postoperatively. All patients underwent electrophysiologic testing, with sustained monomorphic tachyarrhythmias inducible in 7. Three early deaths occurred after this initial evaluation. Among the 9 survivors with nonsustained, nonclinical or noninducible VT, 4 received no antiarrhythmic therapy and remained free of recurrence, whereas of the 5 that received drugs, implantable defibrillators, or both, 2 had spontaneous recurrence. For the surviving subgroup with inducible monomorphic VT, serial drug testing culminated in maintenance therapy with class IA agents or amiodarone, whereas defibrillators were also implanted in 3 patients. Overall, recurrence of life-threatening tachyarrhythmias beyond the immediate postoperative period was seen in 40% of patients with monomorphic clinical tachycardias and inducible sustained monomorphic VT. Ventricular tachyarrhythmias appearing shortly after cardiac surgery demonstrate significant chronicity and resistance to antiarrhythmic drug therapy, while statistically significant predictors of inducibility or their recurrence remain undefined.

Role of electrophysiologic techniques in the selection of antiarrhythmic drug regimens for ventricular arrhythmias.

Programmed electrical stimulation of the heart provides a useful new technique for guiding the selection of antiarrhythmic drug regimens in selected patients with ventricular tachycardia (VT) or ventricular fibrillation. The technique of programmed electrical stimulation has been applied successfully in patients with recurrent sustained VT, out-of-hospital ventricular fibrillation and unexplained syncope in the presence of structural heart disease. The complete suppression of VT induced by programmed electrical stimulation by a drug regimen is highly predictive of freedom from both recurrent VT and sudden death. In addition, this technique may hold promise as a means of assessing the arrhythmogenic effects of antiarrhythmic drugs in selected patients.

Long-term reproducibility of responses to programmed cardiac stimulation in spontaneous ventricular tachyarrhythmias.

Programmed electrical stimulation (PES) of the heart has been used to initiate and terminate ventricular tachyarrhythmias under controlled conditions in patients in whom these arrhythmias have occurred spontaneously. The long-term reproducibility of the response to programmed cardiac stimulation in patients with ventricular arrhythmias is unknown. Seventeen patients with previously documented spontaneously occurring ventricular tachyarrhythmias were evaluated: 5 with nonsustained ventricular tachycardia (VT), 10 with sustained VT and 2 with ventricular fibrillation. The underlying cardiac diagnosis was atherosclerotic coronary heart disease (CAD) in 11 patients, dilated cardiomyopathy in 2 patients, congenital heart disease in 1 patient and no structural heart disease in 3. All patients underwent PES in the absence of antiarrhythmic drug treatment, and patients with inducible VT underwent serial electrophysiologic-pharmacologic testing in an attempt to suppress the arrhythmia. All 17 patients were reexamined with PES at a mean of 18 months (range 2 to 42) after their initial electrophysiologic study, during which time none had a myocardial infarction or intervening cardiac surgery. Repeat electrophysiologic studies, performed in the absence of antiarrhythmic agents, were undertaken because of drug intolerance, availability of new drugs, recurrent arrhythmia or preoperative reevaluation. All 11 patients with CAD had inducible VT on both the first and second electrophysiologic evaluation. Of the 6 patients with no CAD, only 1 had inducible VT on both occasions. Thus, long-term reproducibility of PES-induced VT in patients with stable CAD appears to be high.

Predictors of fracture in the Accufix Atrial "J" lead.

The Accufix atrial lead has a "J"-shaped retention wire at the distal end that has been reported to fracture. Our findings suggest that the more deformed the J, the higher the incidence of fracture.

The differentiation of restrictive cardiomyopathy from constrictive pericarditis.

The differentiation of restrictive cardiomyopathy from pericardial constriction remains a difficult clinical problem. Although the historical, noninvasive, and hemodynamic and angiographic features discussed here provide poor discriminating value when considered individually, a combination of clues may suggest one diagnosis or the other. Endomyocardial biopsy affords the greatest hope of avoiding unnecessary surgical exploration. Thoracotomy continues, however, to be the gold standard by which to make the distinction, carrying with it significant risk in patients with underlying restrictive cardiomyopathy.

Undersensing as a consequence of lead incompatibility: case report and a plea for universality.

Implantation of a single chamber bipolar pulse generator was complicated by transient loss of ventricular sensing, caused by mechanical damage to the unipolar lead connected to the system. A perforation of the insulating sheath was found at the site of the proximal connector block, and undersensing resolved after restoring its integrity with silicone adhesive. The ability to attach an unprotected unipolar lead to a bipolar connector, shared by the Voluntary (VS-1) and International (IS-1) designs, invites the possibility of injury to the insulating sheath by accidental tightening of the proximal screw. There is thus an urgent need for the development and universal adoption of a robust interface standard in lead connector design.

Inability to communicate with ICDs: an underreported failure mode.

The inability to perform telemetry on an ICD may have many potential causes. We report three recently identified cases where such a finding was indicative of unexpected device failure. Two of these cases involved identical failure mechanisms resulting from arcing of current within the high voltage hybrid. This placed the device into a high current state that caused rapid and complete battery depletion. There were no company alerts issued regarding this systematic problem. A multicenter arrhythmia device/lead database would be extremely useful in providing timely and unbiased information concerning device problems.

Optic neuropathy following amiodarone therapy.

Ocular changes during treatment with amiodarone are almost universal but are rarely serious. In this article we describe three patients from a single electrophysiology practice in whom optic neuropathy developed during treatment with amiodarone. All three patients were more than 65 years of age. The doses of amiodarone ranged from 100 to 400 mg/day, and the time intervals between the initiation of the amiodarone therapy and the appearance of first symptoms of optic neuropathy were 5 to 19 months. Two patients had bilateral involvement, and one had only unilateral involvement. Whether this result was due solely to amiodarone therapy, to the underlying poor health of these patients, or to the combination of these two factors is uncertain. These findings prompt us to recommend that all patients who receive amiodarone undergo complete ophthalmologic examinations, including careful evaluation of the ocular fundus regularly during such therapy. No randomized study had been undertaken to determine the true incidence of complications associated with this medication.

Troubleshooting implantable cardioverter defibrillator system malfunctions: the role of impedance measurements.

High impedance measurements may be used to troubleshoot ICD system malfunction. In four different cases a defective system was identified or confirmed by an abnormal impedance: two secondary to lead fractures, one to an adapter faulty connection, and one to a loose set-screw connection. This led to further diagnostic procedures that ultimately localized the difficulty. Though the problems with ICD may be of diverse origins, routine use of impedance measurement for the troubleshooting of these systems may serve as an early sign of malfunction and would point the need for further investigation.

Twiddler's syndrome with transvenous defibrillators in the pectoral region.

Advances in technology have enabled the implantation of defibrillators in the pectoral region. Complications encountered with pacemakers may also be observed with defibrillators. We describe two cases of twiddler's syndrome in patients with defibrillators implanted subcutaneously in the left pectoral region.

Inappropriate shocks delivered by an ICD as a result of sensed potentials from a transcutaneous electronic nerve stimulation unit.

Although the potential for transcutaneous electronic nerve stimulation (TENS) units to interfere with appropriate function of cardiac pacemakers is well documented, an adverse interaction between a TENS unit and an ICD has never been reported. We describe a patient in whom a TENS unit created an electrical artifact that was interpreted by a transvenous ICD as ventricular fibrillation, leading to the delivery of inappropriate therapy. TENS units should be used with caution in patients with ICDs.

Oral mexiletine in the treatment of refractory ventricular arrhythmias: the role of electrophysiologic techniques.

Mexiletine is a useful antiarrhythmic agent for the treatment of ventricular arrhythmias. Its efficacy in suppressing ventricular arrhythmias during serial electrophysiologic evaluation has come under investigation only recently. Experience to date in more than 300 patients suggests that suppression of inducible ventricular arrhythmias by mexiletine either alone or in combination with another antiarrhythmic agent may be achieved in approximately 30% of patients. Furthermore, suppression sometimes may be achieved when mexiletine is tested in combination with a type IA antiarrhythmic or beta-adrenergic blocking agent in patients for whom neither agent alone has been effective. The likelihood of suppressing inducible ventricular tachycardia (VT) with mexiletine therapy alone or in combination may vary as a function of the spontaneous ventricular arrhythmia with which a patient presents at the time of electrophysiologic study; patients presenting with sustained VT appear to have inducible arrhythmias that are more difficult to suppress. A significant incidence of adverse effects attributable to mexiletine has been observed, particularly gastrointestinal and neurologic effects. These side effects, although common, are frequently eliminated by reducing the dosage of the drug and administering the drug with food. A facilitation of arrhythmia induction has also been observed in a small percentage of patients. Early experience suggests that selected patients with ventricular arrhythmias that are refractory to conventional antiarrhythmic agents may derive long-term benefit from chronic therapy with oral mexiletine.

Spurious detection of ventricular fibrillation by a transvenous implantable cardioverter defibrillator during percutaneous transluminal coronary angioplasty.

This case describes another example of inappropriate implantable defibrillator shock. We also show that this phenomenon resulted from electromagnetic current traveling down a coronary wire during coronary angioplasty.