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Biomedical subjects

M Scheinman

Publications and source records attributed to M Scheinman.

At least 55 records · Page 3Linked to original sources
PubMed1986

Interventional electrophysiology: catheter ablation for patients with cardiac arrhythmias.

Catheter ablative techniques have introduced an exciting new chapter of interventional therapy for patients with drug-resistant cardiac arrhythmias. A variety of techniques are presently available, and proper choice depends on proper localization of the tachycardia focus and mechanism of the arrhythmia. These techniques should be performed only in laboratories with personnel experienced in invasive electrophysiologic procedures. Over the past 5 years, we have learned that catheter ablation of the AV junction for patients with drug-resistant supraventricular tachycardia has replaced the need for surgery in these patients. In addition, preliminary experience suggests that the catheter technique may be highly effective for patients with tachycardia incorporating a posteroseptal accessory pathway. The precise role of catheter ablation for patients with atrial or ventricular tachycardia has not been clearly defined.

Arrhythmias, Cardiac↗
PubMed1984

Phase image evaluation of patients with ventricular pre-excitation syndromes.

To localize bypass pathways, left and right ventricular regions were analyzed at rest by phase image analysis in 18 patients with ventricular pre-excitation syndromes. These were compared with image findings in 18 normal subjects. In each of 17 patients with pre-excitation, the site localized on electrophysiologic study correlated closely with the region of earliest ventricular phase angle. This site could be objectively separated from that in normal subjects in each of eight patients with an active left-sided pathway and in both patients with a right-sided pathway. Those with a septal pathway revealed earliest septal phase angle, but could not be separated from normal subjects. In the eight patients with an active left bypass tract, the onset, upstroke and peak of the left ventricular phase histogram preceded those of the right ventricular histogram. Those with a left-sided pathway demonstrated a mean left ventricular phase angle, a difference between mean left and mean right ventricular phase angle and a difference between earliest left and right ventricular phase angles which was significantly less than that in normal subjects (p less than 0.05). These variables presented characteristic converse changes in those with a right-sided pathway. Sequential phase changes in 10 studies suggested "fusion" of normal septal with lateral bypass fronts. Electrocardiographic and electrophysiologic localization of the bypass pathway agreed in only 8 of 14 patients with a recognized delta wave. The phase image represents a new, noninvasive method of evaluating ventricular pre-excitation. The method may provide useful information complementary to that of electrocardiographic and electrophysiologic analysis.

Adolescent↗
PubMed1983

Hemodynamic effects of intravenous amiodarone in patients with depressed left ventricular function and recurrent ventricular tachycardia.

The systemic hemodynamic effects of intravenously administered amiodarone were evaluated in patients with depressed left ventricular function and recurrent sustained ventricular tachycardia. Heart rate decreased linearly up to 1 hour after amiodarone infusion (5 mg/kg). Cardiac index varied in a cubic fashion, diminishing at 10 minutes and returning to baseline by 60 minutes (p less than 0.05). Stroke work index also showed a similar decrease at 10 minutes, which was transient (p less than 0.005). These changes occurred without any significant change in systemic vascular resistance and with slight or no increase in pulmonary capillary wedge pressure, indicating a negative inotropic effect of amiodarone. The depression of left ventricular function in these patients, however, was mild and transient, and intravenously administered amiodarone was tolerated by the vast majority of patients. In two patients with overt heart failure and severely depressed left ventricular ejection fraction and marked hemodynamic abnormalities, profound hypotension occurred during amiodarone therapy; in such patients, therefore, hemodynamic monitoring is preferable. Limited data are available on the hemodynamic effects of orally administered amiodarone, but the determination of left ventricular ejection fraction by radionuclide ventriculography before and during long-term amiodarone administration has shown no reduction of function even in patients with severely reduced myocardial performance.

Administration, Oral↗
PubMed1983

Closed chest permanent atrioventricular block in dogs.

Ten mongrel dogs underwent transcutaneous His bundle ablation by means of pulsed synchronized electrical shocks delivered between an electrode catheter adjacent to the His bundle and a metal plate behind the dog's back. Detailed histologic studies were performed 3 months after induction of stable complete atrioventricular (AV) block in nine dogs. The ventricular response ranged from 35 to 51 beats/min (bpm). Graded increases in overdrive ventricular pacing resulted in graded increases in pacemaker suppression up to a paced cycle length of 450 msec. All dogs showed extensive damage to the approaches to the AV node, the AV node, and the penetrating portion of the common bundle. This technique resulted in complete AV block with typical features of an infranodal pacemaker and correlated with the histologic findings of severe damage to the AV junction. The minimal myocardial damage suggests that this technique may be applicable for control of drug refractory supraventricular arrhythmias in humans.

Animals↗
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

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

The phase image: its relationship to patterns of contraction and conduction.

To determine the relationship of phase changes and abnormalities of ventricular contraction and conduction, we performed phase image analysis of blood pool scintigrams in 29 patients. Eleven patients had no evidence of blood pool contraction or ECG conduction abnormalities, four had contraction abnormalities, seven had abnormal conduction and seven had abnormalities of both variables. The phase delay generally related to the degree of contraction abnormality. The mean phase delay in hypokinetic segments differed from that in normokinetic segments in the same patient (p less than 0.025), the phase delay of akinetic and dyskinetic segments differed from that in normokinetic segments (p less than 0.001) and the phase delay in dyskinetic segments differed from that in akinetic segments (p less than 0.005), but there was a significant overlap in the phase delay in normal and hypokinetic segments. Also, in patients with conduction abnormalities, the minimal associated regional phase delay presented a phase dispersion and a pattern of contraction consistent with the pattern of conduction and different from normal. A single study performed both at rest and with stress demonstrated the effect of heart rate on phase assessment and confirmed the independent effects of contraction and conduction on phase delay. Acquisition and analytic methods should add significantly to the resolution of the phase method.

Arrhythmias, Cardiac↗
PubMed1982

Termination of ventricular tachycardia by carotid sinus massage.

Intracardiac electrophysiologic studies were performed in two patients who had recurrent sustained ventricular tachycardia. In both, the tachycardia was repeatedly terminated by carotid massage. In one patient, intracardiac electrophysiologic studies revealed ventricular tachycardia with 2:1 retrograde ventriculoatrial (VA) block. Carotid massage resulted in alternate Wenckebach retrograde VA conduction terminated by ventricular echo beats. When ventricular echo beats occurred at a coupling interval of 340 - 400 msec, the tachycardia was terminated. Similarly, induced atrial depolarizations (during ventricular tachycardia) produced ventricular capture and terminated the tachycardia when the resultant ventricular coupling interval was 330 - 395 msec. In the second patient, progressively premature atrial or ventricular depolarizations did not terminate the tachycardia. carotid massage had no consistent effect on retrograde VA conduction during ventricular tachycardia, but usually resulted in gradual increases in the tachycardia cycle length (50 - 100 msec) before abrupt termination of the tachycardia. This is the first report documenting termination of ventricular tachycardia by carotid massage alone (i.e., without prior drug intervention); hence, tachycardia termination by simple carotid sinus massage does not prove a supraventricular origin. The mechanism of tachycardia termination was due to ventricular echo beats from retrograde atrioventricular nodal reentry in one patient and to direct vagal effects on either the ventricular muscle or the ventricular specialized conduction system in the other.

Adult↗
PubMed1981

Closed-chest electrode-catheter technique for His bundle ablation in dogs.

A modified quadripolar electrode catheter that had two-thirds of the distal surface insulated with high-voltage plastic was inserted in 10 dogs. After a His bundle potential had been recorded, a synchronized direct-current electrical discharge was delivered between the electrodes showing the largest His bundle deflection using a standard direct-current defibrillator, and a metallic plate was positioned over the dog's back. Complete atrioventricular (AV) block was induced in 9 of 10 dogs, which were followed for 3 mo before being killed. During AV block, the QRS complex was broad and not preceded by a His bundle deflection. The mean control cycle length during AV block was 1,441 +/- 223 ms and decreased to 1,151 +/- 181 ms after exercise, a response that was usually abolished by beta-blockade. Overdrive pacing resulted in pacemaker suppression with gradual rate stabilization after 10-20 beats. There was no evidence of myocardial or valvular damage. This technique provides for a stable model of complete AV block and is suitable for experiments in which heart rate control is required. In addition, this technique may be of value for patients with tachycardia requiring His bundle section.

Angiography↗
PubMed1979

Electrophysiological effects of disopyramide in patients with bundle branch block.

Electrophysiological studies were performed in 22 patients with intraventricular conduction delay before and after intravenous infusion of disopyramide (Norpace), 2 mg/kg. Mean control maximal sinus node recovery time (1039 +/- 187 msec), atrioventricular nodal conduction time (113 +/- 28 msec), and atrioventricular nodal effective refractory periods (349 +/- 67 msec) did not change significantly after administration of disopyramide (1073 +/- 284 msec, 112 +/- 31 msec, and 342 +/- 42 msec, respectively). Mean spontaneous cycle length (756 +/- 146 msec) decreased significantly 5 minutes after disopyramide (717 +/- 124 msec) (p less than 0.05), but not after 30 minutes (734 +/- 142 msec). A small but statistically significant (p less than 0.05) increase occurred after disopyramide in the mean atrial effective refractory period (259 +/- 51 to 280 +/- 53 msec), ventricular effective refractory period (253 +/- 23 to 275 +/- 33 msec), as well as the relative refractory period of the ventricular specialized conduction system (six patients) 433 +/- 78 to 479 +/- 62 msec). Although mean control infranodal conduction time (67 +/- 35 msec) increased 5 minutes after disopyramide (79 +/- 41 msec) (p less than 0.001) (18%), no spontaneous episodes of second-degree or third-degree atrioventricular block were observed. In six patients with premature ventricular depolarizations (greater than or equal to 1/min), the arrhythmia was totally abolished in four, markedly reduced in one, and remained unchanged in one. Disopyramide resulted in significant prolongation of infranodal conduction time as well as in atrial and ventricular refractoriness, but nevertheless appears to be safe in patients with bundle branch block.

Atrioventricular Node↗
PubMed1979

Congenital abnormalities of the conduction system in two patients with tachyarrhythmias.

Serial sections of the conduction system (CS) were performed in two patients with recurrent tachyarrhythmias. Case 1, a 34-year-old female who had dual atrioventricular (AV) nodal pathways with recurrent paroxysmal supraventricular tachycardia, committed suicide. Autopsy revealed an abnormally formed atrial septum with insertion of eustachian valve on the AV part of the pars membranacea. The intercuspid portion of the pars membranacea was muscular. The AV node was located adjacent to the membranous part of the ventricular septum rather than the central fibrous body. In addition, there was an accessory anterior AV node on the parietal wall of the right atrium. Case 2, a 13-year-old boy with history of recurrent ventricular tachycardia, died suddenly. CS revealed a right-sided, markedly septated bundle. The first part of right bundle branch was divided into three parts, which later joined together. Both cases showed fatty infiltration of the atrial septum, more than normal for the age of the patients. The relationship of the recurrent tachyarrhythmias to the congenital abnormalities in the CS in the two cases and the fatty infiltration is reviewed.

Adolescent↗
PubMed1978

Determinants of antegrade echo zone in the Wolff-Parkinson-White syndrome.

Forty-five patients with the Wolff-Parkinson-White syndrome and reciprocating tachycardia which utilized the atrioventricular (A-V) node for antegrade conduction and an accessory pathway for ventriculo-atrial (retrograde) conduction were studied. The extrastimulus technique in the right atrium and coronary sinus at multiple pacing cycle lengths was used. Three types of "echo zones" were defined by the relationship of the antegrade effective refractory period (ERP) of the accessory pathway, the longest coupling interval accompanied by an atrial echo, the ERP of the A-V node, and the functional refractory period of the atrium. Eighteen of 45 patients (40%) had more than one type of echo zone demonstrated by changing either pacing site or pacing cycle length or both. Pacing site and intraventricular conduction delay were found to have important effects on the longest coupling interval accompanied by an atrial echo in those echo zones in which the longest coupling interval accompanied by an atrial echo was less than the antegrade ERP of the accessory pathway. The echo zone is a useful concept to explain the physiology of the common reciprocating tachycardia in patients with the Wolff-Parkinson-White syndrome. However, the echo zone is profoundly affected by pacing site and pacing cycle length. When these variables are changed, many patients can be shown to have more than one type of echo zone. Studies of the echo zone have limited value as therapeutic guides.

Cardiac Pacing, Artificial↗
PubMed1975

Sustained accelerated idioventricular rhythm.

A 73-year-old white man became easily fatigued and hypotensive six weeks after a documented acute inferior myocardial infarction. Continuous ECG monitoring showed a sustained tachycardia with a right bundle branch block pattern. A His bundle electrogram showed no His deflection prior to ventricular activation. The patient was successfully treated with intravenous procaine amide resulting in reversion to sinus rhythm, loss of symptoms, and return of blood pressure to normal levels. The unique aspects of this case and therapeutic considerations in the management of this problem are discussed.

Aged↗