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Biomedical subjects

M M Scheinman

Publications and source records attributed to M M Scheinman.

At least 109 records · Page 6Linked to original sources
PubMed1992

Active compression-decompression resuscitation: a novel method of cardiopulmonary resuscitation.

Chest compression is an important part of cardiopulmonary resuscitation (CPR), but it only aids circulation during a portion of the compression cycle and has been shown to only minimally increase blood flow to vital organs. The purpose of this study was to quantitate the short-term hemodynamic effects of CPR with a hand-held suction device that incorporates both active compression and decompression of the chest. The suction device was applied to the middle of the sternum and compared with standard manual CPR in eight nonventilated anesthetized dogs. Coronary perfusion pressure, systolic and diastolic aortic pressures, right atrial diastolic pressure, and the velocity time integral (an analog of cardiac output), which were obtained by means of transesophageal pulsed wave Doppler echocardiography from the main pulmonary artery, were measured every 30 seconds during CPR. Minute ventilation was measured over the last minute of each CPR technique. Both active compression-decompression CPR and standard CPR were sequentially performed for 2 minutes in random order 30 seconds after induced ventricular fibrillation. The CPR techniques consisted of 100 compressions per minute, with a compression depth of 1.5 to 2 inches and a 50% duty cycle. Coronary perfusion pressure, velocity time integral (cardiac output analog), minute ventilation, and systolic arterial pressure were all significantly improved by active compression-decompression CPR when compared with standard CPR. We conclude that active compression-decompression CPR is a simple technique that appears to improve coronary perfusion pressure, systolic arterial pressure, cardiac output, and minute ventilation in nonventilated animals when compared with standard CPR.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Determination of patch electrode position for the internal cardioverter-defibrillator by cine computed tomography and its relation to the defibrillation threshold.

Cardioverter-defibrillator implantation in 22 consecutive patients after aborted sudden cardiac death was followed by prospective determination of the correct anatomic position of epicardial patch electrodes by chest X-ray study and cine computed tomography; the data were compared with the defibrillation threshold obtained intraoperatively. Patch electrode position was qualitatively graded. Computed tomography improved the assessment as compared with X-ray study in 13 patients (59%), visualizing electrodes in relation to the underlying myocardial and vascular structures. Although the computed tomographic technique provided more precise visualization, its grading of patch position correlated as poorly as that of the X-ray study with the measured acute defibrillation threshold. Three-dimensional reconstruction by computed tomography made it possible to determine quantitatively left ventricular mass (free wall and septum) and the mass encompassed by the patch electrodes. The 34.6 +/- 13.7% (range 12.6 to 61.1%) of the left ventricular mass encompassed by both patch electrodes showed a linear relation to the defibrillation threshold (r = 0.64, p = 0.01). Differentiation of free wall and septal mass in these measurements revealed that the proportion of septal mass encompassed by patch electrodes correlated closely with the defibrillation threshold (r = -0.6, p = 0.019), whereas that of the free wall mass, although significantly larger (35.4 +/- 15.8 vs. 20.6 +/- 15.4 g, p = 0.007), did not. Thus, the position of epicardial patch electrodes could be reliably determined by computed tomography.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Combined use of beta-adrenergic blocking agents and long-term cardiac pacing for patients with the long QT syndrome.

OBJECTIVE: The objective of this study was to review our current experience using a combination of beta-adrenergic blocking agents and long-term cardiac pacing to treat patients with the idiopathic long QT syndrome. BACKGROUND: Patients with the idiopathic long QT syndrome are at high risk for sudden cardiac death. Before combination therapy, 20 of the 21 study patients experienced either cardiac arrest (n = 8) or syncope (n = 18) and 11 had documented polymorphous ventricular tachycardia. Nine of these patients had not responded to isolated beta-blocker therapy and five had not responded to isolated left cervicothoracic sympathectomy. METHOD: All patients were treated with combined beta-blocker therapy and long-term cardiac pacing at a rate designed to normalize the QT interval. RESULTS: Cardiac pacing at rates of 70 to 125 beats/min resulted in shortening of the QT and corrected QT (QTc) intervals from 517 +/- 78 and 541 +/- 62 ms to 404 +/- 37 and 479 +/- 41 ms, respectively. The mean follow-up interval after institution of pacing was 55 +/- 45 months. The only sudden death occurred in a patient who had discontinued beta-blocker therapy. Syncope occurred in four patients, two of whom had interrupted pacemaker function due to lead fracture. Pacemaker problems, partly attributable to the specific rate required for QT interval shortening and to avoidance of T wave sensing, were relatively common. No patient who continued the combination therapy died, but 10% of these patients had a recurrence of symptoms. CONCLUSIONS: Combination therapy with a beta-blocker and cardiac pacing appears to be a highly effective primary therapy for symptomatic patients with the long QT syndrome and to provide excellent adjunctive therapy for patients who require insertion of an automatic internal defibrillator.

Adrenergic beta-Antagonists↗
PubMed1992

Curative percutaneous catheter ablation using radiofrequency energy for accessory pathways in all locations: results in 100 consecutive patients.

Patients with accessory pathway-mediated supraventricular tachycardia have typically been treated with drugs or surgery. Although catheter ablation using high voltage direct current shocks has been used to treat patients with drug-refractory supraventricular tachycardia, there are associated disadvantages, including damage due to barotrauma as well as the need for general anesthesia. Recently, transcatheter radiofrequency energy has evolved as an alternative to direct current shock or surgery to ablate accessory pathways. Percutaneous catheter ablation of 109 accessory pathways with use of radiofrequency energy was attempted in 100 consecutive patients. Patient age ranged from 3 to 67 years. The patients had been treated for recurrent tachycardia with a mean of 2.7 +/- 0.2 antiarrhythmic agents that either proved ineffective or caused unacceptable side effects. In seven patients previous attempts at accessory pathway ablation with use of direct current shock had been unsuccessful. Forty-five (41%) of the pathways were left free wall, 43 (40%) were septal and 21 (19%) were right free wall. Eighty-nine (89%) of the 100 patients had successful radiofrequency ablation at the time of hospital discharge. In all but 12 patients the ablation was accomplished in a single session. Complications attributable to the procedure, but not to the ablation itself, occurred in four patients (4%). No patient developed atrioventricular block or other cardiac arrhythmias. Over a mean follow-up period of 10 months, nine patients had some return of accessory pathway conduction; a repeat ablation procedure was successful in all five patients in whom it was attempted. It is concluded that a catheter ablation procedure using radiofrequency energy can be performed on accessory pathways in all locations. The procedure is effective and safer, less costly and more convenient than cardiac surgery and can be considered as an alternative to lifelong medical therapy in any patient with symptomatic accessory pathway-mediated tachycardia.

Adolescent↗
PubMed1992

Importance of recording the right bundle branch deflection in the diagnosis of His-Purkinje reentrant tachycardia.

Eight of 120 consecutive patients with inducible sustained ventricular tachycardia who were studied at our institution from September 1, 1988 to January 1, 1991, were found to have reentry within the His-Purkinje System as the mechanism of their tachycardias. Two of the eight patients (25%) required the recording of the right bundle branch potential to elucidate the tachycardia circuits. The electrophysiological findings of these two patients are described. In both instances, the diagnosis of supraventricular tachycardia with aberrancy was excluded. In patient 1, a His-bundle electrogram preceded each QRS complex during tachycardia and the His-to-His interval variation preceded changes in QRS intervals. However, recordings from the right bundle branch allowed for exclusion of bundle branch reentry and evidence was found for reentry restricted to the left fascicles. In patient 2, despite instances of dissociation of the His-bundle deflection from the tachycardia, a right bundle branch potential preceded each QRS and spontaneous changes in the interval between successive activation of the right bundle branch preceded changes in ventricular activation. Catheter ablation of the right bundle branch eliminated the tachycardia. It is concluded that the recording of a right bundle branch potential should be included in electrophysiology study of patients in whom there is suspicion of reentry within the His-Purkinje System. Clinically, recognizing these forms of tachycardias can be important because they can be effectively treated with catheter ablation.

Adult↗
PubMed1992

Ablation of ventricular tachycardia using multiple sequential transcatheter application of radiofrequency energy.

Multiple sequential radiofrequency energy was applied in the left and right ventricles of 24 dogs to produce large ablated areas limited to endocardial and subendocardial regions. Endocardial ablation was performed in nine dogs with normal ventricles and 15 that had survived remote myocardial infarcts, three with inducible sustained monomorphic ventricular tachycardia. A quadripolar catheter was positioned either at the site of earliest ventricular activation during induced monomorphic ventricular tachycardia or at circumscribed areas of the left ventricle. Radiofrequency energy was delivered between two adjacent poles of the catheter, successively applying radiofrequency energy to the distal, middle, and proximal electrode pairs; this was repeated 9 to 11 times with the catheter in a slightly different position. A cumulative energy of 9,688 +/- 4,191 joules resulted in an ablated endocardial/subendocardial surface area of 4.7 +/- 2.2 cm2 (range 2.4-10 cm2, maximum depth 4 mm). Sustained tachycardia was not inducible by aggressive programmed ventricular stimulation in the dogs with previously inducible tachycardia, indicating successful ablation of the tachycardia foci. Only seven normal dogs were available for electrophysiological studies; three were used in acute and four in chronic studies. Ventricular tachycardia was not induced in the remaining dogs either before or after radiofrequency ablation, indicating the lack of an arrhythmogenic effect of this method. Histologic examination was performed in all nine normal dogs (five were sacrificed for acute pathological examination) as well as in the 15 with myocardial infarction. The late pathological examination of the radiofrequency lesion in these 19 animals showed homogeneous areas of coagulation necrosis and endocardial proliferation. Thus, this modified technique of radiofrequency ablation produced large homogeneous endocardial/subendocardial scars suitable for treating ventricular tachycardia and showed no evidence of an arrhythmogenic influence.

Animals↗
PubMed1992

Effects of sympathetic stimulation on use dependence of lidocaine, mexiletine, and quinidine in an intact canine model.

The use- or rate-dependent effects of a continuous infusion of lidocaine (n = 6, serum level 3.1 +/- 0.34 micrograms/mL), mexiletine (n = 8, serum level 7.08 +/- 0.90 micrograms/mL), and quinidine (n = 6, serum level 6.8 +/- 1.22 micrograms/mL) were studied in an open chest canine preparation. A use-dependent effect on conduction was assessed by measuring the change in the His to surface ventricular activation (HV) time at differing atrial paced rates during drug infusion. Global sympathetic activation was achieved by nondecentralized left stellate ganglion stimulation (4-10 Hz, 6-12 V, 2 ms) and use dependence at the same cycle lengths was compared. Repolarization times were measured from epicardial monophasic action potentials recorded from the anterior left ventricle throughout the study. There was no significant change in the HV time during control studies with or without left stellate stimulation. Use-dependent slowing of conduction was seen in all studies during drug infusion. This was evident at cycle lengths of 300-190 ms for quinidine and at cycle lengths less than 250 ms for lidocaine and mexiletine. Stellate stimulation attenuated use dependence in all studies. This effect was significant from cycle lengths of 300-190 ms for lidocaine and quinidine and at cycle lengths shorter than 230 ms for mexiletine (p less than 0.05). Stellate stimulation significantly reduced use-dependent prolongation of the HV interval by an average of 60%. During stellate stimulation there was a nonsignificant trend towards cycle length independent shortening of action potential duration both at baseline and in the presence of drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1992

Two-dimensional echocardiographic phase analysis. Its potential for noninvasive localization of accessory pathways in patients with Wolff-Parkinson-White syndrome.

BACKGROUND: In patients with the preexcitation syndrome who are undergoing transcatheter or surgical ablation, accurate localization of accessory pathways is critical. Because preexcitation is known to alter ventricular activation sequence and result in focal areas with presystolic contraction, we investigated whether phase analysis applied to two-dimensional echocardiographic cine loops objectively identifies these focal areas and can be used to localize ventricular insertion sites of accessory pathways. METHODS AND RESULTS: We prospectively obtained phase images in 17 patients (11 males; age range, 11-35 years) during minimal preexcitation in normal sinus rhythm and during maximal preexcitation induced by right atrial pacing. A group of 11 normal subjects (six men; age range, 26-37 years) served as controls. Pathway locations predicted from phase imaging were compared with those predicted from routine 12-lead ECGs, from visual inspection of cine loop images, and from catheter-mounted electrode endocardial mapping. Cross-sectional views in a digital cine loop format were mathematically transformed using a first harmonic Fourier algorithm to obtain the corresponding phase images. Phase angle histograms were derived in eight wall segments. Mean and earliest phase angles were derived by computer analysis to quantitate contraction sequence. We found that during right atrial pacing, phase angles in focal areas markedly deviated from normal--mean phase angles from 33 degrees to 164 degrees, and earliest phase angles from 50 degrees to 180 degrees. Accessory pathways could be precisely localized in 53% of the patients by 12-lead ECG, in 59% by visual inspection of cine loop images, in 82% by phase imaging, and in 94% by a combination of the three methods. CONCLUSIONS: Our results suggest that phase imaging, especially when used in combination with cine loop and 12-lead ECG, can be used to localize ventricular insertion sites of accessory pathways and may be clinically useful as a noninvasive adjunct to endocardial mapping in patients with Wolff-Parkinson-White syndrome.

Adult↗
PubMed1992

Electrophysiological findings and long-term follow-up of patients with the permanent form of junctional reciprocating tachycardia treated by catheter ablation.

BACKGROUND: The permanent form of junctional reciprocating tachycardia (PJRT) commonly presents as recurrent drug-refractory, narrow-complex tachycardia. We studied the efficacy and safety of catheter ablation in treating these patients. METHODS AND RESULTS: Six patients with the diagnosis of PJRT were treated at our institution with direct-current catheter ablation. The study cohort comprised three men and three women with a mean age of 33.8 +/- 4.5 years. The mean time from onset of symptoms to ablation was 129 +/- 44.7 months. All failed multiple drug therapy (mean number of drugs failed was 5.3 +/- 0.5). The left ventricular ejection fractions were calculated by echocardiography and were greater than 60% in all except two patients, whose ejection fractions were 25% and 32%. Symptom duration was significantly longer in those with depressed ejection fraction compared with normal patients (258 versus 64.5 months, p less than 0.01). Electrophysiological findings revealed evidence of an atrioventricular reciprocating tachycardia involving retrograde decremental conduction over an accessory pathway localized to the posteroseptal area. Five patients received two direct-current shocks (250 +/- 16.7 J per shock) via paired electrodes from a catheter positioned just outside the coronary sinus os to a patch placed between the scapulae or on the anterior chest wall. One patient received a single direct-current shock of 300 J. The only complication was the development of complete atrioventricular block in one patient. This patient had previously undergone permanent pacemaker insertion for the sick sinus syndrome. The mean hospital stay after ablation was 2.2 days. Mean peak creatinine phosphokinase after ablation was 352 +/- 58.1 units/l and the MB fraction was 12 +/- 2%. Follow-up echocardiograms or gated nuclear studies showed improvement of ejection fraction in the two patients who presented with depressed ejection fractions. After a mean follow-up of 35.8 +/- 10.3 months, all patients remained free of tachycardia without antiarrhythmic drugs. CONCLUSIONS: We conclude that catheter ablation by using direct current energy appears to be an effective treatment in patients with PJRT.

Adult↗
PubMed1992

Advances in evaluating and treating Wolff-Parkinson-White syndrome.

Interest has increased in the use of new noninvasive modalities, particularly body surface mapping, for localizing accessory pathways in Wolff-Parkinson-White syndrome. New data from invasive studies reviewed here include evidence of decremental conduction and the linking phenomenon in patients with accessory pathways. Risk factors for sudden death, including syncope and atrial fibrillation, are reviewed. The most notable advances involve our ability to offer patients catheter ablation, which has proven to be safe and effective. Both direct current and radiofrequency catheter ablation are discussed.

Death, Sudden, Cardiac↗
PubMed1991

Emergency intracardiac defibrillation for refractory ventricular fibrillation during routine electrophysiologic study.

Ventricular fibrillation refractory to cardiopulmonary resuscitation including multiple transthoracic defibrillations occurred in four patients during 1,215 consecutive ventricular tachycardia induction studies. A technique of emergency intracardiac defibrillation for management of refractory ventricular fibrillation is described. In four patients, stable monomorphic ventricular tachycardia (320 to 570 ms cycle length) was induced during the study and overdrive ventricular pacing resulted in ventricular fibrillation. These patients did not respond to prompt transthoracic defibrillations (5 to 15 attempts/patient) and cardiopulmonary resuscitation, including antiarrhythmic therapy. As a last resort, intracardiac defibrillation was performed with use of a previously inserted standard right ventricular quadripolar catheter as cathode and a posterior skin patch as anode. High energy intracardiac defibrillation pulses (100 to 500 J) delivered from a standard defibrillator successfully terminated each arrhythmia. Intracardiac defibrillation is technically simple and appears effective in terminating refractory ventricular fibrillation in the electrophysiology laboratory. However, further research is necessary to determine the safety and efficacy of this technique, as well as potential applications in other emergency settings.

Aged↗
PubMed1991

Safety and efficacy of oral flecainide therapy in patients with atrioventricular re-entrant tachycardia.

OBJECTIVE: To assess the short- and long-term safety and efficacy of oral flecainide therapy in patients with symptomatic tachycardia and an extranodal accessory pathway. DESIGN: Open-label, uncontrolled trial with a mean follow-up of 24 months. SETTING: Referral-based, teaching medical center. PATIENTS: Sixty-three patients with symptomatic tachycardia and an extranodal accessory pathway. INTERVENTIONS: Patients had electrophysiologic testing before and after the initiation of oral flecainide therapy and were followed long-term for the presence of symptoms, new physical limitations, and adverse effects of therapy. MEASUREMENTS AND MAIN RESULTS: Flecainide therapy prevented or slowed (324 +/- 59 ms to 398 +/- 55 ms; P less than 0.001) inducible sustained atrioventricular reciprocating tachycardia in 44 of 63 patients (70%). Of the 44 patients discharged from the hospital, 33 (75%) have continued to receive flecainide therapy and have shown no adverse effects (mean follow-up, 24 +/- 10 months). Adverse cardiac reactions (proarrhythmia or sinus node suppression) attributable to flecainide occurred in 11 of 63 patients (17%); in 9 (82%) of these 11 patients, events were detected during either in-hospital monitoring or the electrophysiologic study done before discharge. Structural heart disease was detected by two-dimensional echocardiography in 8 of 11 patients who had adverse cardiac events and in 6 of 52 patients who did not have such events (P less than 0.001). Isoproterenol reversed the effects of flecainide therapy in 11 of 21 patients; 7 of the 11 patients had spontaneous clinical recurrences of tachycardia or palpitations during the follow-up period, but these symptoms occurred in only 1 of 10 patients who did not show isoproterenol-induced reversal (P = 0.02). CONCLUSIONS: Oral flecainide therapy was effective in 33 of 63 patients who had tachycardia and an extranodal accessory connection. Hospital monitoring during initial therapy is recommended, and flecainide should be used with caution, if at all, in patients with structural heart disease. An isoproterenol challenge appears to be helpful in predicting late recurrence of tachycardia.

Adolescent↗
PubMed1991

Ablation of the atrioventricular junction with radiofrequency energy using a new electrode catheter.

Percutaneous catheter ablation using radiofrequency energy can be used to interrupt atrioventricular (AV) conduction in patients with supraventricular tachycardia refractory to drugs. Results of radiofrequency ablation of the AV junction using a custom-designed catheter with a large, 3-mm-long distal electrode, 2-mm interelectrode spacing, and a shaft with increased torsional rigidity were compared with those using a standard quadripolar electrode catheter (Bard EP). An electrocoagulator (Microvasive Bicap 4005) supplied unmodulated radiofrequency current at 550 kHz, which was applied between the distal electrode of the ablation catheter and a large skin electrode. With use of the modified catheter, 12 of 13 patients (92%) had persistent complete AV block induced with 7 +/- 5 applications of 18 +/- 6 W of radiofrequency power. In contrast, complete AV block was produced in only 9 of 18 (50%) historical control patients treated with the standard catheter, despite a similar number of applications (7 +/- 5) and power output (16 +/- 4 W). A rise in impedance, due to desiccation of tissue and coagulum formation, occurred earlier (28 +/- 18 vs 52 +/- 24 seconds, p less than 0.001) and more frequently (54 vs 40% of applications, p = 0.047) in patients treated with the standard catheter than in patients treated with the modified catheter. The use of a catheter designed to increase the surface area of electrode-tissue contact allows more radiofrequency energy to be delivered before a rise in impedance occurs and appears to increase the effectiveness of radiofrequency ablation of the AV junction.

Atrioventricular Node↗
PubMed1991

Patients with supraventricular tachycardia presenting with aborted sudden death: incidence, mechanism and long-term follow-up.

A total of 13 (4.5%) of 290 patients with aborted sudden death had either documented (7; 54%) or strong presumptive evidence of supraventricular tachycardia that deteriorated into ventricular fibrillation. Six (46%) of the 13 had an accessory conduction pathway and either atrial fibrillation (5 patients) or paroxysmal atrioventricular (AV) reentrant tachycardia (1 patient) that deteriorated into ventricular fibrillation. Three patients with AV node reentrant tachycardia and four with atrial fibrillation and enhanced AV node conduction presented with supraventricular arrhythmias that deteriorated into ventricular fibrillation. Patients were treated with medical, surgical or catheter ablative procedures designed to prevent recurrences of supraventricular arrhythmias. Four patients received an implanted automatic defibrillator, but none had an appropriate device discharge. Over a follow-up period of 41.6 +/- 33.6 months, 12 patients are alive without symptomatic arrhythmias. One patient died because of severe chronic lung disease and heart failure. Supraventricular tachycardia was the cause of aborted sudden death in approximately 5% of patients referred for evaluation of sudden cardiac death. Treatment directed at prevention of supraventricular tachycardia was associated with an excellent prognosis. Current treatment techniques appear to obviate the need for automatic defibrillator therapy in these patients.

Adult↗
PubMed1991

Value of electrocardiographic leads MCL1, MCL6 and other selected leads in the diagnosis of wide QRS complex tachycardia.

To compare the modified precordial leads MCL1 and MCL6 with the conventional precordial leads V1 and V6 and assess the diagnostic accuracy of selected leads for continuous bedside electrocardiographic (ECG) monitoring, 121 wide QRS complex tachycardias were recorded from 92 patients during cardiac electrophysiologic study. As ascertained from intracardiac recordings, 86 tachycardias were ventricular and 35 were supraventricular with aberrant conduction. Early or late peaking of the predominant QRS deflection in lead MCL6 or V6 proved valuable in diagnosing wide complex tachycardia. An interval of less than or equal to 50 ms from the onset of the QRS complex to the predominant peak (or nadir) indicated supraventricular tachycardia; an interval of greater than or equal to 70 ms indicated ventricular tachycardia. The QRS complexes in leads MCL1 and MCL6 were comparable to those in leads V1 and V6 during sinus rhythm. Significant discrepancies in QRS configuration occurred between the modified and conventional precordial leads during ventricular tachycardia, especially between leads MCL1 and V1; however. these differences did not affect diagnostic accuracy. A single MCL1, V1, MCL6 or V6 lead was equally valuable in the diagnosis of wide complex tachycardia and far superior to a single lead II. A combination of leads (MCL1 + MCL6), (V1 + V6), (V1 + I + aVF) or (V1 + V6 + I + aVF) was superior to a single lead or the routinely monitored lead V1 + II combination.

Bundle-Branch Block↗