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Biomedical subjects

A Kadish

Publications and source records attributed to A Kadish.

At least 55 records · Page 3Linked to original sources
PubMed1991

Current treatment for Wolff-Parkinson-White syndrome: results and surgical implications.

From July 1986 to January 1991, 123 patients with Wolff-Parkinson-White syndrome underwent operation for ablation of aberrant conduction pathways. There were 85 male and 38 female patients ranging in age from 11 months to 68 years. Associated anomalies included Ebstein's anomaly, sudden death syndrome, coronary artery disease, cardiomyopathy, abdominal aortic aneurysm, neurofibromatosis, other arrhythmias, or other complex congenital heart disease. Forty-one patients had multiple accessory pathways. Operative results showed a 7% initial failure rate, which dropped to 3% after reoperation. One patient had undergone previous operation for Wolff-Parkinson-White syndrome at another institution. Procedures performed concomitantly included mitral or tricuspid valve repair or replacement (6), right ventricular conduit replacement, subaortic resection, Fontan repair, corrected transposition repair, coronary artery bypass, and placement of an automatic internal cardioverter defibrillator. There was no operative mortality. Late follow-up is 27 +/- 16 months, and complications included mitral regurgitation and myocardial infarction. By comparison, in the last 12 months 124 patients with the Wolff-Parkinson-White syndrome underwent catheter ablation using radiofrequency current. There were 9 patients with multiple pathways. One hundred twelve patients (90%) had all accessory atrioventricular connections ablated and have remained free of symptomatic tachycardia. There have been 12 failures (10%), of which 5 have had operation and 7 are being treated medically. Mean follow-up is 7 +/- 5 months, and complications included circumflex coronary artery occlusion, excessive bleeding, valve perforation, and cerebral vascular accident.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Monophasic action potential duration during programmed electrical stimulation.

UNLABELLED: To examine changes in monophasic action potential duration (APD) with a pacing protocol similar to that used during electrophysiological testing, action potentials were recorded in vivo from the left ventricular apical endocardium of 12 normal mongrel dogs. The atrioventricular node was ablated and the dogs paced from the anterior right ventricle at a baseline cycle length of 1000 ms between interventions. Mean steady-state APD (APDss) was 266 +/- 7 ms at a pacing cycle length (PCL) of 1000 ms. Two pacing protocols were used. The first consisted of a sudden acceleration in pacing from a cycle length of 1000 ms to one between 300 and 600 ms. The second consisted of an 8-beat train at a cycle length of 400 ms followed by a premature beat at a coupling interval of 280 ms followed by a pause. The inter-train pause varied between 1 second and 32 seconds. With a sudden acceleration in pacing rate, steady-state values for APD at the faster PCLs were significantly smaller than APDss at 1000 ms with a change to cycle lengths of 600 ms (247 +/- 29 ms), 500 ms (229 +/- 21 ms), 400 ms (220 +/- 17 ms), and 300 ms (203 +/- 31 ms; P less than 0.01 for all comparisons). The time constant of the change in APD was shorter at a PCL of 300 ms (14.9 +/- 0.8 s) than 600 ms (20.3 +/- 4.7 s; P less than 0.05). With drive train pacing and incorporating an inter-train pause, the percent drop in steady-state APD compared to APD for the first train ranged from 10.1% with a 1-second inter-train pause to 2.1% with a 32-second pause. The difference in APD between the first drive train and drive trains after at least 3 minutes of pacing when APD had stabilized was not significant for an inter-train pause exceeding 8 seconds. IN CONCLUSION: (1) with a sudden acceleration in pacing rate, endocardial APD in vivo decreases exponentially. The faster the new rate, the shorter the new steady-state APD and the shorter the time constant. (2) When pacing using an 8-beat drive train and an inter-train pause, there is a decremental shortening in APD for pause lengths shorter than 16 seconds. Thus, while performing programmed stimulation using a pause, a conditioning period of at least 2 minutes should be used prior to diastole scanning to allow APD to achieve a steady state.

Action Potentials↗
PubMed1991

Prospective comparison of a conventional and an accelerated protocol for programmed ventricular stimulation in patients with coronary artery disease.

BACKGROUND: This study compared the sensitivity, specificity, and efficiency of a "conventional" and "accelerated" programmed stimulation protocol in 293 patients with coronary artery disease who had a history of sustained or nonsustained monomorphic ventricular tachycardia (VT). METHODS AND RESULTS: In the conventional protocol, one and two extrastimuli were introduced during sinus rhythm and during basic drive trains at cycle lengths of 600 and 400 msec at the right ventricular apex and then at the outflow tract or septum. In the accelerated protocol, one, two, and then three extrastimuli were introduced at each of three basic drive train cycle lengths (350, 400, and 600 msec) at the right ventricular apex; the procedure was repeated at a second right ventricular site. Six hundred thirty-four electrophysiological tests were performed using one of these two protocols either in the baseline state (293 tests) or during drug testing (341 tests). The yield of sustained, monomorphic VT was 89% with the conventional protocol and 92% with the accelerated protocol during baseline tests in patients who had a history of sustained VT (p = 0.05); 20% and 34%, respectively, during baseline tests in patients with a history of nonsustained VT (p = 0.06); and 70% and 77%, respectively, during drug testing (p = 0.2). To induce sustained, monomorphic VT, 10.1 +/- 5.0 (mean +/- SD) protocol steps and 14.4 +/- 8.7 minutes were required with the conventional protocol, compared with 4.0 +/- 3.7 steps and 5.6 +/- 6.1 minutes with the accelerated protocol (p less than 0.001 for each comparison). Among the tests in which sustained, monomorphic VT was induced, sustained polymorphic VT or ventricular fibrillation was induced more often with the conventional protocol (3.6%) than with the accelerated protocol (0.9%, p = 0.05). CONCLUSIONS: The efficiency of programmed stimulation can be improved by the early use of a basic drive train cycle length of 350 msec and three extrastimuli. Compared with a conventional stimulation protocol, the accelerated protocol used in this study reduces the number of protocol steps and duration of time required to induce monomorphic VT by an average of more than 50% and improves the specificity of programmed stimulation without impairing the yield of monomorphic VT.

Cardiac Pacing, Artificial↗
PubMed1991

Catheter modification of the atrioventricular junction with radiofrequency energy for control of atrioventricular nodal reentry tachycardia.

BACKGROUND: The utility of transcatheter application of radiofrequency energy to eliminate atrioventricular nodal reentrant tachycardia (AVNRT) was investigated. METHODS AND RESULTS: Thirty-nine patients (mean age, 53 +/- 20 years; range 14-86 years) with medically refractory AVNRT underwent perinodal ablation with radiofrequency energy. A custom-designed 6F catheter with a large (3-mm-long) distal electrode and interelectrode pacing of 2 mm was used in the majority of cases. The catheter used for ablation was initially positioned across the tricuspid anulus to obtain the largest His bundle electrogram, then withdrawn to obtain the largest atrial:ventricular electrogram ratio, with a small His bundle electrogram (less than or equal to 100 microV). Each application of radiofrequency energy (350-550 kHz, 16.2 +/- 5.2 W) was stopped after 60 seconds or if PR prolongation or an impedance rise was noted. The endpoints of the procedure were persistent modification of atrioventricular nodal conduction (either first-degree atrioventricular block or impairment of ventriculoatrial conduction) and noninducibility of AVNRT before and during isoproterenol administration. Radiofrequency energy was applied a mean of 6.8 +/- 3.5 times per session. After a mean follow-up of 8 +/- 3.0 months, 32 of the 39 patients (82%) have been free of AVNRT, and did not have high grade AV block. Three patients (8%) developed complete atrioventricular block and had pacemakers implanted. Two patients had unsuccessful initial procedures, and two patients had initially successful ablations but had recurrences of tachycardia 4-6 weeks later. Elimination of AVNRT appeared to be due to effects on the retrograde fast pathway in most patients. CONCLUSIONS: Radiofrequency ablation of the perinodal right atrium appears to be safe and effective for treatment of typical AVNRT:

Atrioventricular Node↗
PubMed1991

A prospective comparison of class IA, B, and C antiarrhythmic agents in combination with amiodarone in patients with inducible, sustained ventricular tachycardia.

BACKGROUND: Clinical experience suggests that combinations of antiarrhythmic agents provide more effective control of ventricular tachyarrhythmias than does therapy with single agents. METHODS AND RESULTS: Antiarrhythmic and electrophysiological effects of three class I antiarrhythmic agents, one from each subclass A, B, and C, were assessed in single use and in combination with amiodarone in patients with inducible, sustained ventricular tachycardia that was not suppressed by monotherapy with these agents. Thirty-one patients underwent an electrophysiology test on four occasions: at baseline; after 2-4 days of treatment with quinidine, mexiletine, or encainide; after 2 weeks of treatment with 1,200 mg/day amiodarone; and last, after 2-4 days of treatment with both amiodarone and the previously tested class I agent. The combination of a class I agent and amiodarone prevented the induction of sustained ventricular tachycardia in only one of 31 (3%) patients. Ventricular tachycardia became hemodynamically stable in 11 of 31 (34%) patients because of a marked prolongation in the tachycardia cycle length. It increased from 323 +/- 39 to 423 +/- 84 msec (n = 11, p less than 0.01) by adding encainide to amiodarone therapy, and it showed a tendency to lengthen when quinidine was added to amiodarone (from 373 +/- 77 to 425 +/- 58 msec; n = 10, NS). Each class I agent increased amiodarone-induced depression in myocardial conduction, but the extent of the additional depression seemed to differ among the three subclasses. Ventricular refractoriness was increased by all class I agents when used in combination with amiodarone, although not by mexiletine or encainide when used alone. CONCLUSIONS: Class I antiarrhythmic agents slow ventricular conduction and increase ventricular refractoriness when used in combination with amiodarone. When amiodarone and class I drugs by themselves do not suppress the induction of ventricular tachycardia, the combination of amiodarone and a class I agent seldom results in noninducibility; however, it often lengthens the ventricular tachycardia cycle length and may render the ventricular tachycardia hemodynamically stable.

Amiodarone↗
PubMed1990

Feasibility and cost savings of outpatient electrophysiologic testing.

The feasibility of outpatient electrophysiologic testing was examined by reviewing 100 consecutive outpatient tests performed in 95 patients. Seventy-one of the patients (75%) had no underlying heart disease. The electrophysiologic tests were performed to evaluate supraventricular tachycardias (n = 47), nonsustained ventricular tachycardia (n = 20), unexplained syncope (n = 21), palpitation (n = 9) or intermittent heart block (n = 2). A mean of 2.8 +/- 0.5 6F electrode catheters were inserted through a femoral vein. An electrode catheter was inserted into a subclavian or internal jugular vein in 28 tests and a 5F cannula was inserted into a femoral artery to monitor the blood pressure in 20 tests. The results of 61 tests (61%) were abnormal. Patients were monitored for a mean of 3.8 +/- 1.2 h after the procedure and then discharged. No complications occurred. For cost analysis a subgroup of 60 of these patients was matched for age, gender, heart disease and indication for electrophysiologic testing with a group of 60 patients who underwent electrophysiologic testing as inpatients. Physicians' fees for the two groups were similar; however, the mean hospital charge was $5,845 +/- 3,763 for the inpatient group compared with only $2,120 +/- 1,244 for the outpatient group (p less than 0.001). Thus, outpatient electrophysiologic testing is feasible and safe and results in substantial cost savings in patients without life-threatening arrhythmias.

Adult↗
PubMed1990

Determinants of the ventricular rate during atrial fibrillation.

Determinants of the ventricular cycle length during atrial fibrillation were examined in 52 patients. Thirty-three patients had structural heart disease and none had an accessory atrioventricular (AV) connection. The AV node effective and functional refractory periods, the shortest atrial pacing cycle length associated with 1:1 conduction, the AV node conduction time and indexes of concealed conduction in the AV node were measured in the baseline state (36 patients) and after modification of sympathetic tone by infusion of isoproterenol or propranolol (8 patients each). Atrial fibrillation was then induced with rapid atrial pacing, and the mean, shortest and longest ventricular cycle lengths were measured. Variables that correlated most strongly with the mean RR interval during atrial fibrillation were the AV node effective refractory period (r = 0.93; p less than 0.001), AV node functional refractory period (r = 0.87; p less than 0.001) and shortest atrial pacing cycle length associated with 1:1 conduction (r = 0.91; p less than 0.001). The AH interval during sinus rhythm (r = 0.74; p less than 0.001) and during atrial pacing at the shortest cycle length with 1:1 conduction (r = 0.52; p less than 0.001) had weaker correlations. Measures of concealed conduction did not improve the prediction of the mean or longest ventricular cycle length during atrial fibrillation. In conclusion, the refractory periods and conductivity of the AV node are the best indicators of the potential of the node to transmit atrial impulses to the ventricles during atrial fibrillation. The degree of concealed conduction in the AV node is a less important determinant of the mean ventricular rate during atrial fibrillation.

Atrial Fibrillation↗
PubMed1990

An automatic microcomputer system for analysis of monophasic action potentials.

A computer system for rapid measurement and analysis of monophasic action potentials (MAPs) recorded in vivo was developed. MAPs recorded from the epicardium of mongrel dogs using a contact electrode were digitized by analog-to-digital conversion at a sampling rate of 1 kHz per channel for computer data acquisition. Activation time was detected using a sliding 10-point window at the location where the average positive dV/dT exceeds an adjustable threshold value in order to eliminate spurious detection due to baseline variability or motion artifact. Action potential duration (APD) was determined at 50% and 90% (APD50, APD90) repolarization levels at the first sample point below these detection levels. In addition, a tangent algorithm (APDtan) that detects peak negative dV/dT during repolarization was developed. APDtan was determined from the location of onset of activation to the intersection of tangent and baseline. APDtan allowed estimation of APD in the presence of subsequent premature beats when APD90 was not measurable. To validate activation time measurements, 4,600 action potentials were analyzed during fixed rate pacing. Over a range of paced coupling intervals from 200 to 1000 msec, an R2 value of 0.99968 and a slope of 0.9959 were obtained by linear regression between paced and calculated intervals. To validate APD measurements, 5035 action potentials were analyzed in five animals during fixed rate pacing (longer than 3 minutes) when action potential duration should be constant. Average coefficient of variation of 1.25%, 1.65%, and 1.14% were obtained for APD50, APD90, and APDtan, respectively. This algorithm provides a rapid and accurate method to analyze MAP activation and duration for basic physiological studies such as the determination of initiation of arrhythmias.

Action Potentials↗
PubMed1989

Electrophysiological studies on cardiac catheter ablation.

Clinical and animal investigations have pointed out that high energy electrical shocks are associated with the development of cardiac arrhythmias and with variable success in permanent ablation. The effects of electrode configuration and location on the size of the recorded electrogram was investigated to help explain variable catheter ablation results. We analyzed the cellular effects of catheter ablation shocks and found depression of resting potential, action potential amplitude, dV/dt and action potential duration. The most severe effects were noted with high current densities in tissues located between the cathode and anode. Damage was worse nearest the cathode. Similar cellular studies were completed using argon laser photoablation. Again, there was a decrease in resting potential, action potential amplitude and dV/dt. Laser energy led to a more focal region of myocardium void of action potentials and the border zone of injury was smaller. We also investigated the effects of lower energy shocks (1 to 10 joule) on cardiac tissues. Using microelectrodes, we observed that the membrane potential can "hang up" at the depolarized levels for varying periods of time and that conduction is altered during this membrane "hang-up" period. The duration and membrane hang-up level correlated with shock intensity and shock duration. Sequential shocks resulted in additive membrane "hang-up". We believe that membrane hang-up may be associated with brief arrhythmias observed following catheter ablation since conduction, refractoriness and excitability are all altered.

Action Potentials↗
PubMed1989

Activation patterns in healed experimental myocardial infarction.

The maximum amplitude of vector loops formed by summing orthogonally recorded bipolar electrograms has been shown to reflect the direction of activation in cardiac muscle. To investigate whether components of vector loops could provide information about different activation directions in local areas of myocardium, we correlated "instantaneous vectors" with isochronal activation patterns in an in vitro preparation of experimental myocardial infarction. In thirteen 3 mm x 3 mm regions studied (from 11 tissues), at least 16 microelectrode impalements with a minimum density of 0.8 mm between sites were made. In seven situations in which notched, irregular, and prolonged duration electrograms were present, vector loops pointed in the same general direction throughout their entire time course. In these preparations, microelectrode impalements demonstrated only a single major direction of activation. In five of six areas in which multidirectional vector loops were present, two or more separate local directions of activation corresponded to the directions of the vector loop. Instantaneous vectors were then used to analyze propagation patterns in vivo in 10 animals with 2-4-week-old experimental myocardial infarction. Of 150 sites in the 10 animals, 13% contained more than one major local direction of activation. In 11 markedly abnormal sites, electrograms were recorded during pacing from four sites around the recording probe. When comparing electrogram characteristics from the four sites, a mean difference of 5.9 mV in electrogram amplitude and 19.1 msec in electrogram duration (coefficient of variation, 27% for amplitude and 22% for duration) was found. In only two of the 11 sites was it found that the same number of activation directions occurred from all pacing sites. We conclude: 1) Instantaneous components of vector loops accurately represent local directions of cardiac activation at differing times. 2) Most areas of experimental myocardial infarction have only one major direction of activation despite the presence of abnormal electrograms. 3) In some regions, however, two major local directions of activation can be identified within a relatively local area. 4) Geometric activation patterns in experimental myocardial infarction are markedly dependent on initial activation direction.

Action Potentials↗
PubMed1988

Interaction of fiber orientation and direction of impulse propagation with anatomic barriers in anisotropic canine myocardium.

We developed a computer model of the interaction of impulse propagation with anatomic barriers in uniformly anisotropic tissue. Its predictions were confirmed experimentally by using an in vitro cut to create a 6 X 1-mm anatomic barrier in 12 canine epicardial strips. The model predicted that long, thin barriers located parallel to the direction of impulse propagation would have little effect in delaying conduction regardless of the arrangement of cardiac fibers. In this situation, the mean experimental ratio of postcut to control conduction times across the barrier was 1.05:1.00 in 10 tissues. When impulses were proceeding perpendicular to an anatomic barrier, significant distal conduction delay was predicted and found to occur only when the conduction from pacing to recording sites was initially longitudinal to fiber orientation (mean experimental ratio, 2.34:1.00 in five tissues) but not transverse to fiber orientation (ratio, 1.08:1.00 in five tissues). We conclude that the direction of initial impulse propagation and the orientation of myocardial fibers have large effects on the degree to which anatomic barriers delay activation in cardiac tissue. These findings may have implications for the participation of anatomic barriers in reentrant circuits.

Animals↗
PubMed1988

Effects of cellular uncoupling on conduction in anisotropic canine ventricular myocardium.

Experiments were performed on canine superfused ventricular epicardial tissue slices to determine the effects of 1.0-2.0 mM heptanol, an uncoupling agent, on conduction longitudinal and transverse to myocardial fiber orientation. Conduction velocities were measured between proximal and distal pairs of epicardial electrodes oriented transverse and longitudinal to the direction of a conducted wavefront evoked by pacing at a basic cycle length of 2,000 msec from one margin of the tissue before and after the addition of heptanol. In a separate group of tissues, the dual bipolar orthogonal electrode was used to sequentially map epicardial activation at 40 to 45 sites in a 1 cm x 2 cm area before and 30 minutes after the introduction of heptanol. In a third group of tissues, transmembrane potentials were recorded with standard microelectrode techniques to determine the effects of heptanol on action potential characteristics. Heptanol did not significantly effect action potential amplitude or maximum rate of depolarization. After 1.0 mM heptanol, conduction velocity began to decrease in 1-2 minutes and reached a steady state in 15-20 minutes. Conduction velocity in the longitudinal direction decreased from a control value of 0.56 +/- 0.13 to 0.46 +/- 0.10 M/sec (+/- SD) at 30 minutes after heptanol (p = 0.005). In the transverse direction, it decreased from 0.24 +/- 0.09 to 0.17 +/- 0.05 M/sec (p = 0.002). The ratio of longitudinal to transverse conduction velocities increased from 2.54 +/- 1.00 to 2.94 +/- 0.82 (p = 0.042). Thus, heptanol preferentially slowed conduction in the transverse direction. Because heptanol did not greatly influence active membrane properties, we used cable equations to calculate the time course of the change in effective junctional resistivity, which rose from 133.2 omega.cm before heptanol to 312.2 omega.cm 30 minutes after heptanol administration. We conclude that heptanol slows conduction velocity by selectively increasing junctional resistivity. The preferential slowing of conduction in the transverse direction is most likely due to the fact that more junctional resistances are encountered per unit distance in the transverse than in the longitudinal direction.

Action Potentials↗
PubMed1985

Chemoprevention of cervix cancer: Phase I-II: A feasibility study involving the topical vaginal administration of retinyl acetate gel.

A Phase I-II clinical trial has been conducted with a retinyl acetate (RA) gel applied cervicovaginally in women having a histopathologic lesion diagnosed as mild or moderate dysplasia. With informed consent, volunteer subjects were observed and followed with Pap smears and colposcopy in a standardized protocol involving a self-administered 7-day treatment course for three successive menstrual cycles. Varying dosages of RA including placebo, 3, 6, 9, and 18 mg per 6 g of an inert vehicle were employed. A total of 50 subjects were monitored for local and systemic side effects. No intolerable side effects or disturbing toxicity was reported or detected at any of these doses. With the 18-mg dosage, significant discomfort was reported by all women. Despite associated side effects and a considerable patient effort involved in carrying out the self-administration of the gel, a high level of compliance was achieved in this trial. It has been established that women will voluntarily participate in an intervention clinical trial to determine whether retinyl acetate is an alternative method of therapy of presumed precancerous lesions of the cervix. The analysis of the side effects of the gel at the various dosage concentrations favors the selection of the 9-mg dosage for a multicenter Phase III clinical trial to determine efficacy.

Colposcopy↗
PubMed1981

Influence of anti-mouse interferon serum on the growth and metastasis of tumor cells persistently infected with virus and of human prostatic tumors in athymic nude mice.

Baby hamster kidney or HeLa cells form tumors in 100% of athymic nude mice. When such cells are persistently infected (PI) with RNA viruses, such as mumps or measles virus, the tumor cells either fail to grow or form circumscribed benign nodules. Neither the parental nor the virus PI tumor cells form invasive or metastatic lesions in nude mice. Previous studies have indicated a correlation between the susceptibility of virus-PI tumor cells in vitro and the cytolytic activity of natural killer (NK) cells and their failure to grow in vivo. Because interferon (IF) is the principal regulatory molecule governing the differentiation of NK cells, it was possible to test the relevance of the IF-NK cell system in vivo to restriction of tumor growth by treatment of nude mice with anti-IF globulin. This treatment was shown to reduce both IF production and NK activity in spleen cells. Both parental and virus-PI tumor cells grew and formed larger tumors in nude mice treated with anti-IF globulin than in control nude mice. The viral-PI tumor cells and the uninfected parental cells formed tumors in treated mice that were highly invasive and often metastatic. Some human tumor types have been notoriously difficult to establish as tumor lines in nude mice (e.g., primary human prostatic carcinomas). When transplanted into nude mice treated either with anti-IF globulin or anti-lymphocyte serum, two prostatic carcinomas grew and produced neoplasms with local invasiveness and some metastases. The results are consistent with the view that interferon may be important in restricting the growth, invasiveness, and metastases of tumor cells by acting indirectly through components of the immune system, such as NK cells.

Animals↗
PubMed1980

Application of transesophageal echocardiography to continuous intraoperative monitoring of left ventricular performance.

Transesophageal M mode echocardiography was used for continuous monitoring of left ventricular dimensions in 21 patients (11 with valvular and 10 with coronary heart disease) undergoing open heart surgery. Echocardiograms were recorded in six stages of the procedure and simultaneous measurements of cardiac output (with dye dilution) and atrial pressures were made. Measurements of left ventricular diameters with the transesophageal technique correlated excellently with the corresponding measurements obtained with the standard parasternal method. In patients with volume overload, surgical correction was accompanied by a decrease in diastolic dimension, velocity of circumferential fiber shortening, mid wall stress and end-diastolic stiffness, and an increase in cardiac output. Pericardial and chest wall closures generally caused a significant decrease in cardiac output, and correlated with a decrease in diastolic diameter and an increase in the stiffness constant of the left ventricle. Thus, the decrease in cardiac output may have been due to decreased distensibility of the ventricular cavity secondary to mechanical restriction by the pericardium and chest wall. Pericardial opening caused a significant delay in septal motion that was reversed by closing the pericardium. This study confirms the validity of transesophageal echocardiography and its usefulness in monitoring changes in ventricular function during cardiac surgery.

Adult↗