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Biomedical subjects

M R Jazayeri

Publications and source records attributed to M R Jazayeri.

At least 19 recordsLinked to original sources
PubMed1999

Ventricular arrhythmias, electrophysiologic studies, and devices.

Because of the high incidence of heart disease in the elderly, ventricular tachyarrhythmias are not infrequent. Determining the nature and extent of the underlying heart disease and identifying precipitating causes is required prior to instituting long-term therapy. Recent studies suggest that for hemodynamically unstable ventricular tachyarrhythmias, mortality is lower with the implantable cardioverter-defibrillator compared with pharmacologic therapy. This benefit is likely to be more modest in the elderly because of competing cardiac and noncardiac causes of death. For similar reasons, the favorable results reported with the prophylactic use of the implantable cardioverter-defibrillator are likely to be attenuated in the elderly.

Aged↗
PubMed1999

Reversing the initial phase polarity in biphasic shocks: is the polarity benefit reproducible?

The effect of initial phase polarity (IPP) reversal using biphasic shocks on DFT at the time of implantation of implantable cardioverter defibrillator and the reproducibility of this effect during predischarge testing was evaluated in a randomized fashion. Twenty-two patients with ventricular tachycardia or ventricular fibrillation (VF) who received either the Medtronic 7219D (7 patients), 7219C (12 patients), 7223 (1 patient), or CPI Ventak MINI (2 patients) were studied. The DFT was determined in a randomized fashion at implantation and during predischarge testing using a binary search protocol. Initial shock was delivered at 12 J. If successful, subsequent shock was delivered at 6 J, following which the shock was incremented or decremented by 3 J depending upon the success. The DFT for right ventricular (RV)- and RV + IPP was 10.9 +/- 4.1 J and 11.1 +/- 4.0 J, respectively, at implant (P = ns) and 9.7 +/- 4.3 J and 8.4 +/- 6 J, respectively, (P = ns) at predischarge testing. Of the six patients who had better DFT with RV + at implantation, only one patient maintained the benefit during predischarge testing. The differences observed in IPP in individual patients may not be demonstrable during repeated testing. These findings may have implications on how these devices should be programmed.

Adult↗
PubMed1998

Spontaneous reinitiation of atrial fibrillation following transvenous atrial defibrillation.

Spontaneous reinitiation of atrial fibrillation (AF) has not been systematically looked at in patients undergoing transvenous AF. This study involved 11 patients, the mean age 60 +/- 8 years, 3 male and 8 female, in whom transvenous atrial defibrillation successfully converted AF to sinus rhythm. Eight patients had paroxysmal AF and three patients had chronic persistent AF for 4 weeks or more. Four patients were taking antiarrhythmic medications at the time of testing. Multipolar transvenous catheters were positioned inside the coronary sinus, right atrium, and the right ventricle. Atrial defibrillation testing was performed using the METRIX atrial defibrillation system in nine patients and the Ventritex HVSO2 in the remaining two patients. A total of 64 therapeutic shocks (range 3-11) were delivered in the 11 patients, and 31 of these successfully converted AF to sinus rhythm. In four patients spontaneous AF was reinitiated following 12 successful transvenous atrial defibrillation episodes. The mean time to reinitiation of AF following shock delivery and restoration of sinus rhythm was 8.26 +/- 5.25 seconds, range 1.8-19.9 seconds. All 12 episodes of spontaneous AF were preceded by a spontaneous premature atrial complex. The coupling interval of the premature atrial complexes was 443 +/- 43 ms, range 390-510 ms. None of the patients taking antiarrhythmic medications or those demonstrating no premature atrial complexes had spontaneous reinitiation of AF. In conclusion, spontaneous reinitiation of AF can occur in a significant proportion of patients with AF undergoing transvenous atrial defibrillation. This phenomenon is preceded by the occurrence of atrial premature complex. Findings of this study may have significant clinical implications.

Adult↗
PubMed1998

Optimization of shocking lead configuration for transvenous atrial defibrillation.

INTRODUCTION: High atrial defibrillation energy requirements (ADER) in patients with chronic atrial fibrillation (AF) may limit the acceptance of transvenous atrial defibrillation. We evaluated an optimized defibrillation electrode configuration that could help to reduce the ADER in patients with AF. METHODS AND RESULTS: We tested ten different configurations in nine dogs with AF (3.33+/-2.92 days) induced by rapid atrial pacing. The configurations were: right atrial (RA) appendage as anode and coronary sinus (CS) as cathode; RA and innominate vein (I) as anode to CS (cathode); RA-CS (anode) to I (cathode); I-CS (anode) to RA (cathode); RA and left lateral subcutaneous patch (P) as anode to CS (cathode); RA-CS (anode) to P (cathode); P-CS (anode) to RA (cathode); superior vena cava (SVC) and CS (anode) to RA (cathode); RA-CS (anode) to SVC (cathode); and RA-SVC (anode) to CS (cathode). ADER was defined as the voltage needed to defibrillate the atria in 10% to 90% of 20 consecutive shocks. Three lead systems had ADER lower than the RA (anode) to CS (cathode) configuration, which required a mean of 143+/-58 volts. These three were: RA-SVC (anode) to CS (cathode) 103+/-29 V; I-CS (anode) to RA (cathode) 129+/-39 V; and P-CS (anode) to RA (cathode) 130+/-38 V. The remaining configurations had ADER higher than the RA (anode) to CS (cathode) configuration. CONCLUSION: Adding an additional shocking electrode may reduce ADER when compared with the RA (anode) to CS (cathode) configuration. This concept could be incorporated into future implantable atrial defibrillators or used for refractory patients undergoing temporary transvenous cardioversion.

Animals↗
PubMed1998

Implantable atrial defibrillator for atrial fibrillation.

Atrial fibrillation is a common problem. Pharmacological and nonpharmacological approaches have limited therapeutic efficacy in many patients. Low energy transvenous atrial defibrillation using catheters positioned inside the right atrium and cornonary sinus has been shown to be efficacious in converting atrial fibrillation to sinus rhythm. We report the successful use of this technology in an implantable form in a patient with symptomatic atrial fibrillation. The patient could be kept in sinus rhythm using an implanted atrial defibrillator.

Atrial Fibrillation↗
PubMed1997

Ventricular tachycardia in valvular heart disease: facilitation of sustained bundle-branch reentry by valve surgery.

BACKGROUND: The clinical characteristics of sustained monomorphic ventricular tachycardia (SMVT), when it develops after valve surgery, have not been described. METHODS AND RESULTS: Between 1985 and 1996, 31 patients (30 men and 1 woman) who had undergone valve surgery were found to have inducible SMVT. Nine patients (29%) had sustained VT due to bundle-branch reentry (BBR) (group 1). Four of these patients had normal left ventricular function, and VT with a right bundle-branch morphology was inducible in 4 patients. Group 2 included 20 patients with inducible myocardial (ie, non-BBR) VT. Coronary artery disease was present in 15 group 2 patients (75%) due to atherosclerotic (n=12) and nonatherosclerotic (n=3) causes. Two patients had both inducible sustained BBR and myocardial VT (group 3). Sustained BBR VT occurred significantly earlier after valve surgery (median, 10 days) than the onset of postoperative myocardial VT (median, 72 months; P<.005). CONCLUSIONS: Myocardial VT was the most common type of inducible SMVT in patients with valvular heart disease. The majority of these patients had underlying coronary artery disease and significant left ventricular dysfunction. However, in almost one third of the patients, sustained BBR VT was the only type of inducible SMVT. This type of VT was facilitated by the valve procedure occurring within 4 weeks after surgery in most patients. In these patients, left ventricular function was relatively well preserved, and the right bundle-branch block type of BBR was frequently induced. Because a curative therapy can be offered to these patients (ie, bundle-branch ablation), BBR should be seriously considered as the mechanism of VT in patients with valvular heart disease, particularly if the arrhythmia occurs soon after valve surgery.

Adult↗
PubMed1997

Comparison of outcome of implantable cardioverter defibrillator implantation in patients with severe versus moderately severe left ventricular dysfunction secondary to atherosclerotic coronary artery disease.

This study was undertaken to assess the feasibility and clinical outcome of implantable cardioverter-defibrillators (ICDs) among patients with coronary artery disease and left ventricular ejection fraction (LVEF) of <20%. The morbidity, mortality, and the long-term survival of 117 patients with LVEF of <20% (group 1) were compared with 321 patients with LVEF of 20% to 40% (group 2). Mortality in the first 30 days after ICD implantation was 0% for group 1 and 0.6% in group 2. Actuarial survival (all cause) at the end of 2, 4, and 5 years were 83%, 70%, and 62%, respectively, in group 1 and 90%, 80%, and 71% in group 2 (p = 0.05). Fifty-five patients (47%) in group 1 and 126 patients (39%) in group 2 received appropriate shocks during follow up. Among the patients in group 1, the overall survival at 2 years after an appropriate shock from an ICD was 92% for patients <60 years of age, 77% for patients ages 60 to 69, and 53% for patients >70 years old. Although the overall survival of patients in group 1 was slightly lower compared with those in group 2, in a multivariate analysis, the EF was not an independent predictor of poor survival. The ICD can be implanted with acceptable operative morbidity and mortality in selected patients with LVEF of <20%.

Aged↗
PubMed1997

Safety of atrial defibrillation shocks synchronized to narrow and wide QRS complexes during atrial pacing protocols simulating atrial fibrillation in dogs.

BACKGROUND: The potential ventricular proarrhythmic effect of atrial defibrillation shocks (ADS) remains a concern with automatic internal atrial defibrillation. Optimal R-wave synchronization alone may not be sufficient to prevent the induction of ventricular fibrillation (VF). METHODS AND RESULTS: The proarrhythmic effect of ADS synchronized to normally conducted QRS complexes (NQRS) and to supraventricular complexes with left or right bundle-branch block (L/RBBB) was investigated in a canine atrial pacing study. Short-long-short, single premature, and burst pacing protocols from the high right atrium were performed at baseline, during isoproterenol infusion, and after intravenous procainamide. The ADS were delivered between decapolar catheters in the coronary sinus and lateral right atrium. They were initially delivered 20 milliseconds (ms) after the end of the last conducted QRS complex and then scanned decrementally through that complex until VF was induced. For NQRS complexes, VF occurred only when the ADS were delivered at or before the onset of the QRS complex and never during the complex itself. In the presence of LBBB or RBBB, VF was induced by ADS delivered at the onset of or within the first 45 ms of the QRS complex in 16 animals. The longest RR (VV) intervals preceding ADS-induced VF were 345 ms at baseline and 380 ms after procainamide. CONCLUSIONS: In this study, ADS synchronized to NQRS complexes appeared to be safe regardless of the preceding RR interval. In the presence of LBBB or RBBB, RR intervals preceding the ADS of >345 ms at baseline and >380 ms in the presence of procainamide would have been required to avoid VF. Alternatively, ADS delivered 50 ms after the onset of the RV electrogram appeared to be safe in all circumstances regardless of the preceding RR interval.

Animals↗
PubMed1997

Efficacy of the implantable cardioverter-defibrillator in the elderly.

OBJECTIVES: We sought to assess the effect of advanced age on the outcome of patients with an implantable cardioverter-defibrillator (ICD). BACKGROUND: ICDs are effective in preventing sudden cardiac death in susceptible patients, but their beneficial effect on survival is attenuated by the high rate of nonsudden cardiac death in those treated. Although advanced age is an important variable in determining cardiovascular mortality, its impact on the outcome of patients with an ICD has been inadequately studied. METHODS: We performed multivariate analysis of a data base consisting of 769 consecutive patients with an ICD. Seventy-four patients > or = 75 years old at ICD implantation (Group 1) were compared with the remaining 695 patients (Group 2). RESULTS: The two groups were similar in clinical presentation, left ventricular function and gender distribution. The mean follow-up time was 29 and 42 months, respectively, for patients in Group 1 and Group 2. Actuarial survival at 4 years was 57% in Group 1 versus 78% in Group 2 (p = 0.0001). This difference was primarily due to a higher rate of nonsudden cardiac death in Group 1. On multivariate analysis, age > or = 75 years, New York Heart Association functional class III, left ventricular ejection fraction < 30% and appropriate shocks during follow-up were independently associated with increased mortality (odds ratio 3.56, 1.8, 1.6 and 1.39, respectively). CONCLUSIONS: Among patients with similar functional class and ejection fraction, the mortality risk is increased threefold in those > or = 75 years old at the time of ICD implantation. Extrapolation of results from younger patients is likely to overestimate ICD benefit in the elderly.

Age Factors↗
PubMed1997

The effect of biphasic waveform tilt in transvenous atrial defibrillation.

Atrial defibrillation can be accomplished using low energy shocks and transvenous catheters. The biphasic waveform tilt required to achieve optimal atrial defibrillation thresholds (ADFTs) is, however, not known. The effect of single capacitor biphasic waveform tilt modification on ADFT was assessed in 20 patients. Following AF induction the defibrillation pulses were delivered between the catheters positioned in the coronary sinus and the right atrium. The single capacitor biphasic waveform shocks, delivered over the same pathways, consisted of 65% tilt (65/65 biphasic waveform) to produce an overall tilt of 88%, or 50% tilt (50/50 biphasic waveform) to produce an overall tilt of 75%. Although 65/65 biphasic waveform delivers more energy, the shorter duration 50/50 biphasic waveform reduced stored energy ADFT 21%, from 1.34 +/- 0.82 J with 65/65 biphasic to 1.06 +/- 0.81 J. These differences were not statistically significant. Nine patients had lower ADFT with 50/50 biphasic waveform while five patients had lower ADFT with 65/65 biphasic waveform. Equivalent reduction in ADFT was seen in the remaining six patients. The ADFT was 0.83 +/- 0.65 J when both tilts were considered. In conclusion, biphasic waveform tilt modification may affect the ADFT in an individual patient. The optimal biphasic waveform for ADFT is not known.

Adult↗
PubMed1997

The effect of polarity of the initial phase of a biphasic shock waveform on the defibrillation threshold of pectorally implanted defibrillators.

The effect of initial phase polarity on the DFT of two pectorally implanted biphasic ICDs was tested in a randomized, prospective manner at the time of implantation. Twenty-two consecutive patients with VT-VF who received either the Medtronic PCD 7219C Jewel device (10 patients) or PCD 7219D Jewel device (12 patients) were studied. DFT testing was performed in a standard step-down manner. Both initial phase polarities--initial defibrillation current flowing from active can/SVC coil +/- subcutaneous patch) to the RV coil (RV coil to active can/SVC (RV+)--were tested in random order. The mean DFT achieved with RV+ compared with RV-was lower for the 7219C patient group (6.6 +/- 3.1 vs 10.8 +/- 5.5 J; P = 0.007). A similar trend was observed for the 7219D group, though the difference did not reach statistical significance (12.0 +/ 4.0 vs 16.3 +/- 7.3 J; P = 0.07). Seven of the 10 patients in the 7219C group had a lower DFT with RV+, while the initial phase polarity made no difference in 3. In the 7219D group, 7 patients had a lower DFT using RV+, 2 patients had a lower DFT using RV-, and the initial phase polarity made no difference in 3. In conclusion, this study demonstrates that changing the polarity of the initial phase of a biphasic shock waveform can have a significant impact on the DFT achieved at the time of ICD implantation.

Aged↗
PubMed1997

Efficacy of midodrine hydrochloride in neurocardiogenic syncope refractory to standard therapy.

INTRODUCTION: Some patients with neurocardiogenic syncope continue to have recurrent syncope or presyncope despite the use of currently available drug therapy. The purpose of this study was to determine whether midodrine hydrochloride, a selective adrenergic agonist, could be effective in patients resistant to, or intolerant of, currently used medications in the treatment of neurocardiogenic syncope. METHODS AND RESULTS: Eleven patients with a history of recurrent syncope or presyncope in whom hypotension with syncope or presyncope could be provoked during head-up tilt testing were included. There were 4 men and 7 women with a mean age (+/-SD) age of 34 +/- 13 years. In all patients, standard therapy with beta-adrenergic receptor blocking agents, ephedrine, theophylline, disopyramide, fludrocortisone, and sertraline hydrochloride, was either ineffective, poorly tolerated, or contraindicated. Midodrine was initially administered orally at a dose of 2.5 mg three times daily. After adjustment of dosage over 2 to 4 weeks, patients were followed-up clinically. Midodrine was discontinued in one patient because of side effects. Frequency of syncope or presyncope during the 3 months prior to starting treatment was compared during a mean follow-up of 17 +/- 4 weeks after starting treatment with midodrine. There was significant (P < 0.01) reduction in syncopal and presyncopal episodes on midodrine. Five patients had complete resolution of symptoms, while four patients had significant improvement. Symptoms did not improve in one patient. CONCLUSIONS: Midodrine hydrochloride can be effective in preventing recurrent symptoms in selected patients with neurocardiogenic syncope unresponsive to, or intolerant of, standard drug therapy.

Administration, Oral↗
PubMed1996

Feasibility of atrial fibrillation detection and use of a preceding synchronization interval as a criterion for shock delivery in humans with atrial fibrillation.

OBJECTIVES: This study assessed the feasibility of detecting atrial fibrillation (AF) and delivery of appropriately timed R wave shocks using an implantable atrial defibrillator. BACKGROUND: For atrial defibrillation therapy to be feasible in an implantable form, AF must be detected in a specific fashion, and the risk of ventricular proarrhythmia should be minimized. METHODS: Eleven patients with AF underwent testing with an implantable atrial defibrillator (METRIX 3000 Automatic Atrial Defibrillator, InControl, Inc.). Wideband electrograms (EGMs) were recorded from the right ventricular (RV) bipolar catheter and from the multipolar catheters located in the right atrium (RA) and coronary sinus (CS). Atrial fibrillation detection was performed using two serial algorithms-quiet interval analysis and baseline crossing analysis-that detect atrial activity on the RA-CS channel. Ventricular sensing using a minimal preceding synchronization interval of 500 ms as a criterion for synchronous shock delivery was performed from filtered RV and RV-CS EGMs. RESULTS: The AF detection algorithms were applied to 53 AF data segments and 18 normal sinus rhythm data segments. Atrial fibrillation was detected appropriately in 49 instances, and the specificity for detecting AF and normal sinus rhythm was 100%. Synchronization criterion efficacy was assessed by delivering shock markers and shocks. Of the 2,025 R waves processed, 557 (27.5%) were marked as suitable for shock delivery. In addition, 69 therapeutic and 11 test shocks were delivered during AF. All shock markers and shocks were delivered synchronously with the R wave, and the synchronization criterion was never violated. CONCLUSIONS: Atrial fibrillation can be detected in a specific fashion using the RA-CS lead configuration and serial detection algorithms for atrial sensing. The delivery of properly timed shocks is feasible and should minimize the risk of ventricular proarrhythmia.

Adult↗
PubMed1996

Functional bundle branch block as a delayed manifestation of retrograde concealment in the His-Purkinje system.

INTRODUCTION: The mechanism of functional bundle branch block induced at the onset of supraventricular tachycardia (SVT) is well established. However, no data exist to address the underlying mechanism of functional bundle branch block occurring in the second beat of SVT, when the first beat is conducted with a narrow QRS morphology and preceded by ventricular stimulation. METHODS AND RESULTS: Two patients showing such a phenomenon form the basis of this report. Patient 1 with AV nodal reentrant tachycardia of the common variety persistently demonstrated functional right bundle branch block in the second SVT complex when a short train of ventricular pacing was introduced during SVT. This occurred without any discernible change in the SVT cycle length. Patient 2 had a manifest posteroseptal accessory pathway and inducible orthodromic reentrant tachycardia. Functional bundle branch block during propagation of the second SVT complex invariably occurred either in the left bundle when SVT was induced by a bundle branch reentrant complex during premature ventricular stimulation, or in the right bundle when SVT was induced with a short train of ventricular pacing. The development of functional bundle branch block was preceded by minimal or no cycle length variations in the His-bundle inputs. CONCLUSION: These observations suggest that the type of functional bundle branch block occurring in the second SVT complex as a de novo phenomenon may be related to the relative timing of the retrograde penetration of the right versus left bundle during ventricular pacing or bundle branch reentrant complex. Therefore, due to its longest cycle length of activation and refractoriness, the earliest site of retrograde penetration is the most likely site of functional block during propagation of the second SVT complex. This delayed manifestation of retrograde concealment may provide new information regarding the electrophysiologic behavior of the His-Purkinje system.

Adolescent↗
PubMed1995

Comparison of monophasic and biphasic defibrillating pulse waveforms for transthoracic cardioversion. Biphasic Waveform Defibrillation Investigators.

All transthoracic defibrillators on the US market use nominally monophasic shock waveforms. However, biphasic waveforms have a lower defibrillation threshold than monophasic waveforms for transthoracic defibrillation of animals and for defibrillation of humans by implantable cardioverter defibrillators. The relative efficacies of Edmark monophasic and Gurvich biphasic transthoracic cardioversion waveforms (200 J into 50 omega) were compared for transthoracic cardioversion in 171 patients undergoing electrophysiologic study for evaluation of ventricular arrhythmias. Patients were randomized in a blinded fashion to receive either a monophasic or a biphasic waveform for the initial shock for conversion of induced ventricular arrhythmias (ventricular fibrillation [VF] = 53, monomorphic ventricular tachycardia [VT] = 80, polymorphic VT = 30, ventricular flutter = 8). Delivered energies for the Edmark and Gurvich waveforms were 215 +/- 11 and 171 +/- 11 J, respectively. There were no significant differences in patient characteristics, use of antiarrhythmic agents, arrhythmia cycle length, or duration of arrhythmia prior to shock for monophasic and biphasic waveform groups. The first shock for all arrhythmias was successful in 75 of 88 patients (85.2%) for the monophasic waveform compared with 81 of 83 patients (97.6%) for the biphasic waveform, p = 0.0054. The first shock for VF was successful in 22 of 28 patients (78.6%) for the monophasic waveform compared with 25 of 25 (100%) for the biphasic waveform, p = 0.0241. The Gurvich biphasic waveforms delivering a mean of 171 J were superior to Edmark monophasic waveforms delivering a mean of 215 J for transthoracic cardioversion of arrhythmias of short duration. This finding may have important implications for the development of future transthoracic defibrillators.

Adult↗