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Biomedical subjects

F Morady

Publications and source records attributed to F Morady.

At least 361 records · Page 20Linked to original sources
PubMed1983

Clinical characteristics and results of electrophysiologic testing in young adults with ventricular tachycardia or ventricular fibrillation.

Thirty-one patients 16 to 40 years of age (mean +/- SD = 30.7 +/- 7 years) had one or more episodes of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Underlying cardiac abnormalities consisted most commonly of cardiomyopathy (nine), long QT syndrome (LQTS) (five), and mitral valve prolapse (five); no identifiable heart disease was found in four patients. Programmed ventricular stimulation induced VT in only one of four patients with the LQTS but induced VT in 64% of 22 patients with other abnormalities. Chronic drug treatment was based either on serial electropharmacologic testing or was empiric when electrophysiologic testing failed to provoke an arrhythmia. Using this approach, we found a 13% incidence of recurrent VT and a 10% mortality over a follow-up period of 18.1 +/- 13.9 months. In young adults with VT or VF, an underlying cardiac abnormality can usually be found. Extensive evaluation should be performed to uncover the underlying cardiac abnormality as this may influence chronic management.

Adolescent↗
PubMed1983

Rapid method for determination of shunt ratio using a thermodilution technique.

A new technique using thermodilution by which shunt ratio can be rapidly and conveniently determined in patients with left-to-right intracardiac shunts is described. A flow-directed balloon-tip thermistor catheter was positioned in the pulmonary artery to measure cardiac output in 20 patients with left-to-right intracardiac shunts. Shunt ratio measured by the Fick technique (Qp:QSF) varied between 1.3:1 and 3.6:1. Early recirculation was seen on the downslope of the thermodilution curves (TC). The first-pass curve before the point of early recirculation was extrapolated to the baseline and the area inscribed by this portion of the TC (A) was measured by planimetry. The area inscribed by the entire TC (A + B) was also measured by planimetry. Shunt size was determined by calculating the ratio (A + B):A. Shunt ratio determined by this technique (Qp:QSTh) correlated well with Qp:QSF (r = 0.89). The thermodilution technique provides a simple, rapid, and accurate method for determining the magnitude of left-to-right intracardiac shunts.

Cardiac Catheterization↗
PubMed1983

Electrophysiologic testing in the management of patients with the Wolff-Parkinson-White syndrome and atrial fibrillation.

Twenty patients with the Wolff-Parkinson-White (WPW) syndrome and 1 or more episodes of symptomatic atrial fibrillation (AF) due to rapid anterograde bypass tract conduction underwent electrophysiologic testing. The mean ventricular rate during spontaneous AF was 242 +/- 56 beats/min (+/- standard deviation) and the shortest preexcited R-R interval was 194 +/- 40 ms. Six patients underwent surgical bypass tract ablation and 14 were treated medically, based on the results of electropharmacologic testing. Over a mean follow-up period of 35 +/- 19 months (+/- standard deviation), only 1 patient treated medically had a recurrence of minimally symptomatic AF. The successful chemoprophylaxis of symptomatic AF was associated with the inability to induce AF and atrioventricular reciprocating tachycardia during drug testing (7 patients) or with the induction of AF with a ventricular rate less than 200 beats/min and a shortest preexcited R-R interval of greater than 250 ms (7 patients). Electrophysiologic testing can identify a subgroup of patients with WPW and AF in whom medical therapy is a suitable alternative to bypass tract ablation.

Adolescent↗
PubMed1983

Electrophysiologic mechanism of exercise-induced sustained ventricular tachycardia.

To elucidate electrophysiologic mechanism of exercise-induced ventricular tachycardia (VT), electrophysiologic studies were performed in 12 patients in whom sustained VT had developed during treadmill exercise testing. Six patients had arteriosclerotic coronary heart disease, 3 had cardiomyopathy, and 3 had no clinical evidence of organic heart disease. All patients had had documented episodes of sustained VT related to exertion and had experienced dizziness, syncope, or both. In addition, 3 patients had had nonfatal cardiac arrest. Electrophysiologic studies provoked paroxysms of sustained VT identical to those observed during treadmill exercise testing in 10 patients and provoked ventricular flutter/fibrillation in 1. Seven patients had VT suggestive of a reentrant mechanism, as the VT could be readily initiated with programmed ventricular extrastimulation or terminated by ventricular overdrive pacing, or both. Three patients had VT suggestive of catecholamine-sensitive automaticity. The VT could not be initiated with programmed electrical stimulation, but it could be provoked by intravenous isoproterenol infusion; furthermore, the VT could not be terminated with ventricular overdrive pacing, but it could be abolished by discontinuing isoproterenol infusion. Reproduction of VT in these 10 patients allowed serial pharmacologic testing in selecting an effective antiarrhythmic regimen. Thus (1) exercise-induced VT can be caused by either reentry or catecholamine-sensitive automaticity, and (2) electrophysiologic studies are of use in defining the underlying mechanism of exercise-induced sustained VT.

Adolescent↗
PubMed1983

Long-term follow-up of patients with recurrent unexplained syncope evaluated by electrophysiologic testing.

Electrophysiologic testing was performed in 53 patients with recurrent syncope that remained unexplained despite a thorough neurologic and noninvasive cardiac evaluation. Fifteen patients had no structural heart disease, 9 had mitral valve prolapse and 29 had structural heart disease other than mitral valve prolapse. Nonsustained ventricular tachycardia was induced in 15 patients (28%), sustained ventricular tachycardia was induced in 9 (17%), ventricular fibrillation was induced in 4 (8%) and sinus node function was abnormal in 2 (4%). Female sex and lack of structural heart disease were independently associated with a negative electrophysiologic study (p less than 0.001). Patients with inducible ventricular tachycardia or ventricular fibrillation were treated with drugs selected on the basis of the results of electropharmacologic testing. The recurrence rate of syncope was 43% over a 31 +/- 10 month period (mean +/- standard deviation) of follow-up in patients with a negative electrophysiologic study, 40% over a 22 +/- 6 month period in patients with inducible nonsustained ventricular tachycardia, 0% over a 30 +/- 12 month period in patients with inducible sustained ventricular tachycardia and 25% over a 21 +/- 10 month period in patients with inducible ventricular fibrillation. In patients with recurrent unexplained syncope undergoing electrophysiologic testing, a potential cause of syncope is least likely to be found in women without structural heart disease. The results of programmed ventricular stimulation must be interpreted with regard to the method of induction of ventricular tachycardia and the type of ventricular tachycardia induced. The excellent response rate in patients with inducible sustained ventricular tachycardia whose therapy is guided by the results of electropharmacologic testing suggests that sustained ventricular tachycardia is a clinically significant response.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiodarone↗
PubMed1983

Electrophysiologic studies in patients with bundle branch block.

A total of 401 patients with chronic bundle branch block underwent electrophysiologic studies and were followed for a mean of approximately 30 months. Patients with an infranodal conduction time (H-Q) greater than or equal to 70 ms had a significantly higher incidence of progression to spontaneous second-degree or third-degree atrioventricular (AV) block (12%) compared with those with H-Q less than 70 ms (3.5%). The incidence of AV block was 25% for those with H-Q greater than or equal to 100 ms. Although the incidences of all deaths and cardiac deaths were higher for the H-Q greater than or equal to 70 ms group, there was no statistically significant difference in the incidence of sudden deaths in the two groups. A subgroup of 77 patients underwent prophylactic pacemaker insertion based on the presence of transient neurologic symptoms and/or a prolonged H-Q interval. We found no significant difference in the incidence of relief of symptoms or incidence of cardiac or sudden deaths between paced and unpaced groups. A subgroup of 25 patients with syncope underwent ventricular stimulation studies and ventricular tachycardia was induced in 14. We conclude that a markedly prolonged H-Q interval (greater than or equal to 100 ms) may be of value in detection of spontaneous AV block. Prophylactic pacing is of no value in either relief of symptoms or prolongation of life. Complete electrophysiologic studies, including ventricular stimulation studies, are indicated for patients with bundle branch block and syncope.

Aged↗
PubMed1983

Amiodarone in the management of patients with ventricular tachycardia and ventricular fibrillation.

Fifty-eight patients with symptomatic ventricular tachycardia (VT) or ventricular fibrillation (VF) were treated with amiodarone. All had clinical episodes of VT/VF or inducible VT during electropharmacologic testing despite treatment with maximum-tolerated doses of conventional antiarrhythmic agents. Chronic treatment with amiodarone was begun at a dose of 800-1000 mg per day. Thirty-two patients were also treated with a previously ineffective conventional agent. Thirty patients underwent programmed ventricular stimulation after 2.6 +/- 1.7 months (mean +/- S.D.) of treatment with amiodarone at a mean daily dose of 588 +/- 155 mg. VT was induced in 25 patients (sustained in 20, nonsustained in five). Seventeen patients had a recurrence of VT or VF after 0.5-9 months of treatment with amiodarone (fatal in seven, non-fatal in 10). Forty-one patients (71%) had no recurrence of symptomatic VT or VF while being treated with amiodarone (mean follow-up period, 17.1 +/- 12.4 months). Among the 25 patients who had inducible VT with programmed ventricular stimulation while being treated with amiodarone, 19 patients (76%) have had no recurrence of symptomatic VT or VF over a follow-up period of 21.5 +/- 7.3 months. Ambulatory electrocardiographic recordings obtained after one week of treatment with amiodarone were not helpful in predicting clinical response. Twenty-two patients (38%) developed ataxia and/or an intention tremor which improved with a decrease in the amiodarone dose. Amiodarone, either by itself or in combination with conventional antiarrhythmic drugs, has a significant therapeutic effect in high risk patients with refractory VT. The finding of inducible VT during electropharmacologic testing in patients taking amiodarone does not preclude a favorable clinical response. Neurologic toxicity is common in patients treated with 600-800 mg per day of amiodarone.

Amiodarone↗
PubMed1983

Extent of atrial participation in atrioventricular-reciprocating tachycardia.

Twenty-one patients with atrioventricular (AV) bypass tracts underwent electrophysiologic studies. The bypass tract was left-sided in 15 patients, septal in five and right-sided in one patient. Orthodromic AV-reciprocating tachycardia was induced in all 21 patients, with a mean tachycardia cycle length of 342 +/- 59 msec. The introduction of single stimuli in the high right atrium during tachycardia resulted in simultaneous dissociation of the high right atrial and low septal atrial electrograms in nine patients. In six patients, high right atrial overdrive pacing during tachycardia resulted in simultaneous dissociation of the high right atrial and low septal atrial electrograms for two to five consecutive beats. All patients in whom the low septal atrial electrogram was dissociated from the tachycardia had a left-sided bypass tract. In no patient was the coronary sinus atrial electrogram dissociated from the tachycardia by high right atrial pacing. Dissociation of the low septal atrial electrogram (as recorded in the His bundle electrogram) from AV-reciprocating tachycardia suggests that the portion of the right atrium adjacent to the AV node may not be a necessary link in the tachycardia circuit. This observation suggests that the site of entry of left-sided impulses into the AV node may be different from that of right-sided impulses.

Cardiac Pacing, Artificial↗
PubMed1983

Effects of verapamil on ventricular tachycardias possibly caused by reentry, automaticity, and triggered activity.

To define the role of verapamil in the treatment of ventricular tachycardia (VT), we studied 21 patients with chronic recurrent VT. Electrophysiologic studies were performed before and during intravenous infusion of verapamil (0.15 mg/kg followed by 0.005 mg/kg per min). On the basis of the mode of VT initiation and termination, we identified three groups of patients: (a) 11 patients had VT suggestive of reentry, as VT could be initiated with ventricular extrastimulation and terminated with overdrive ventricular pacing. Verapamil did not affect the inducibility and cycle length of VT. (b) 7 patients had VT suggestive of catecholamine-sensitive automaticity as VT could not be initiated with programmed electrical stimulation but could be provoked by isoproterenol infusion. Moreover, the VT could not be converted to a sustained sinus rhythm with overdrive ventricular pacing and it resolved only with discontinuing isoproterenol infusion. Verapamil exerted no effects on VT. (c) 3 patients had VT with electrophysiologic characteristics suggestive of triggered activity related to delayed afterdepolarizations. Characteristically, after attaining a range of cycle lengths, the sinus, atrial or ventricular paced rhythm could initiate VT without ventricular extrastimulation. The first beat of VT invariably occurred late in the cardiac cycle with a premature coupling interval 0-80 ms shorter than the preceding QRS cycle length; the premature coupling interval gradually decreased as the sinus, atrial or ventricular paced cycle length progressively shortened. Of note, verapamil completely suppressed VT inducibility in these three patients. These observations lead us to suggest that verapamil does not affect VT caused by reentry and catecholamine-sensitive automaticity but is effective in suppressing VT caused by triggered activity related to delayed afterdepolarizations in humans.

Adolescent↗
PubMed1982

Catheter-induced ablation of the atrioventricular junction to control refractory supraventricular arrhythmias.

Five patients with recurrent bouts of supraventricular tachycardia proved resistant or became intolerant of both conventional and experimental drugs. These patients were subjected to a new procedure involving delivery of DC shocks to an electrode catheter positioned adjacent to the His bundle. Complete atrioventricular (AV) block was produced in all, one patient died suddenly six weeks after shock therapy, and the remainder had complete AV block with follow-up intervals ranging from four to 12 months. Shock therapy was associated with mild elevations of creatine phosphokinase MB (31 +/- 18 units), but there was no hemodynamic evidence of tricuspid insufficiency. If this new technique proves safe and effective, it should supplant the need for open heart surgical procedures for His-bundle ablation.

Adult↗
PubMed1982

Permanent pacemaker implantation in the cardiac catheterization laboratory: the subclavian vein approach.

During a 36-month period, 171 permanent pacemaker procedures were performed in the cardiac catheterization laboratory by invasive cardiologists. This included 111 initial pacemaker system implants, via the percutaneous subclavian vein approach, 45 pulse generator changes, and 15 miscellaneous procedures. In no case did subclavian vein puncture result in pneumothorax, hemothorax, or brachial plexus injury. In patients undergoing initial lead placement, the dislodgment rate was 0.8% over a 16-month follow-up period. The reoperation rate for causes other than premature battery depletion was 5.4% during the first 12 months. The implantation of permanent pacemakers can be safely and effectively accomplished by experienced invasive cardiologists in the cardiac catheterization laboratory. In our series not only was continuity of patient care improved, but also medical costs were reduced.

Adult↗
PubMed1982

Phase image characterization of ventricular contraction in left and right bundle branch block.

The phase image is a computer-derived functional image, based on the analysis of the time versus radioactivity curve in each pixel location of the multiple gated blood pool scintigram. Within the ventricular regions of interest, the phase angle is roughly equivalent to the time of onset of counts reduction or to the time of onset of ventricular contraction and is expressed in degrees from 0 to 360 degrees. A gray scale-coded image of such a regional phase angle, the phase image, can be looked on as a map of sequential contraction. This method was applied in 33 patients without severe contraction abnormality including 16 patients with normal conduction, 9 with right bundle branch block and 8 with left bundle branch block. In patients with normal conduction the pattern of phase angle distribution, representing the pattern of ventricular contraction, was homogeneous and symmetric in both the left and right ventricles. Analysis in this normal group indicated a slight but significant difference between the mean (+/- standard deviation) phase angle of the left ventricle (8.5 +/- 11.8 degrees) and that of the right ventricle (13.6 +/0 12.9 degrees, p = 0.01). There was a slight, but nonsignificant difference between mean intrapatient left and right ventricular phase angle onset (1.9 +/- 6.5 degrees). The mean phase angle of the right ventricle in patients with right bundle branch block (27.6 +/- 14.2 degrees) and of the left ventricle in those with left bundle branch block (21.9 +/- 14.0 degrees) was delayed compared with that in patients with normal conduction (p less than 0.05 for both). The mean intrapatient difference between left and right ventricular mean phase angles in patients with normal conduction (-5.2 +/- 6.8 degrees) was significantly different from that in patients with right (-21.8 +/- 10.3 degrees, p less than 0.001) or left (21.8 +/- 6.8 degrees, p less than 0.001) bundle branch block. The mean intrapatient difference between onset of left and right ventricular phase angles was also significantly different from normal in patients with right (-10.6 +/- 7.5 degrees, p less than 0.005) or left (18.7 +/- 8.3 degrees, p = 0.01) bundle branch block. Although phase imaging is not without artifactual error, this study demonstrates that the phase image can characterize familiar conduction abnormalities. It presents the potential for application as a general noninvasive tool in the investigation of the timing and sequence of ventricular contraction in patients with normal or abnormal ventricular activation.

Adult↗
PubMed1982

An accurate means of detecting and characterizing abnormal patterns of ventricular activation by phase image analysis.

The ability of scintigraphic phase image analysis to characterize patterns of abnormal ventricular activation was investigated. The pattern of phase distribution and sequential phase changes over both right and left ventricular regions of interest were evaluated in 16 patients with normal electrical activation and wall motion and compared with those in 8 patients with an artificial pacemaker and 4 patients with sinus rhythm with the Wolff-Parkinson-White syndrome and delta waves. Normally, the site of earliest phase angle was seen at the base of the interventricular septum, with sequential change affecting the body of the septum and the cardiac apex and then spreading laterally to involve the body of both ventricles. The site of earliest phase angle was located at the apex of the right ventricle in seven patients with a right ventricular endocardial pacemaker and on the lateral left ventricular wall in one patient with a left ventricular epicardial pacemaker. In each case the site corresponded exactly to the position of the pacing electrode as seen on posteroanterior and left lateral chest X-ray films, and sequential phase changes spread from the initial focus to affect both ventricles. In each of the patients with the Wolff-Parkinson-White syndrome, the site of earliest ventricular phase angle was located, and it corresponded exactly to the site of the bypass tract as determined by endocardial mapping. In this way, four bypass pathways, two posterior left paraseptal, one left lateral and one right lateral, were correctly localized scintigraphically. On the basis of the sequence of mechanical contraction, phase image analysis provides an accurate noninvasive method of detecting abnormal foci of ventricular activation.

Adult↗
PubMed1982

Electrophysiologic drug testing in patients with malignant ventricular arrhythmias: importance of stimulation at more than one ventricular site.

Sixty-four patients with symptomatic ventricular tachycardia or ventricular fibrillation underwent right ventricular apical programmed stimulation and had no inducible ventricular tachycardia during drug testing. Thirty patients (Group I) did not undergo left ventricular stimulation. Left ventricular stimulation in 38 drug trials induced no ventricular tachycardia in 50% (Group IIA), nonsustained ventricular tachycardia in 24% (Group IIC). Patients in Groups I, IIA, and IIB received chronic antiarrhythmic drug therapy based on the results of electrophysiologic drug testing. Patients in Group IIC underwent further drug testing until sustained ventricular tachycardia was no longer inducible and were then entered into Group IIA or IIB; 4 patients in whom the induction of sustained ventricular tachycardia could not be suppressed by any drug regimen tested were excluded from long-term follow-up. The duration of follow-up (mean +/- standard deviation) was 15.8 +/- 1.5 months in Group I, 13.6 +/- 3.7 months in Group IIA, and 12.1 +/- 4.9 months in Group IIB. Recurrence rates of symptomatic ventricular tachycardia or sudden death were 27% in Group I, 0% in Group IIA, and 20% in Group IIB (p less than 0.02 for Group IIA versus Group I and p greater than 0.05 versus Group IIB). If only right ventricular apical stimulation is performed during electrophysiologic drug testing in patients with malignant ventricular arrhythmias, approximately 50% of drug trials may be incorrectly judged as suppressing the induction of ventricular tachycardia. Drug therapy that suppresses ventricular tachycardia induction with both right and left ventricular programmed stimulation results in a significantly better clinical response than therapy based on the results of only right ventricular apical stimulation.

Adult↗
PubMed1982

Electrophysiologic testing in the evaluation of patients with syncope of undetermined origin.

Thirty-two patients were prospectively evaluated for syncope (recurrent in 26 patients) with conventional neurologic and cardiovascular testing without elucidation of a cause. All patients underwent invasive electrophysiologic studies to assess sinus nodal function, atrioventricular conduction, and the inducibility of supraventricular and ventricular tachycardia (VT). Eleven patients (34%) were found to have laboratory-induced VT, 5 patients (15%) had evidence of sinus nodal dysfunction, 1 patient (3%) had infra-His atrioventricular block during atrial pacing, and 1 patient (3%) had probable quinidine-related VT. The remaining 14 patients had no detectable abnormalities during electrophysiologic study. After a mean follow-up period of 21.3 +/- 1.2 months, 10 of the 11 patients with inducible VT were asymptomatic while receiving laboratory-directed antiarrhythmic therapy, and 1 patient died from ventricular fibrillation after discontinuing the chosen antiarrhythmic regimen. Five of the remaining 7 patients with an electrophysiologic abnormality were asymptomatic after implantation of a permanent pacemaker or alteration of previous drug therapy, or both. The 14 patients with a normal electrophysiologic study were treated empirically, with recurrent syncope occurring in 4 of these patients during the follow-up period. Invasive electrophysiologic studies provided a presumptive diagnosis in 56% of patients with syncope of undetermined origin. Previously unsuspected VT accounted for 61% (11 of 18) of the detected abnormalities. Therapy specific for the electrophysiologic abnormality was usually successful in preventing recurrent syncope.

Adult↗