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Biomedical subjects

W H Maisel

Publications and source records attributed to W H Maisel.

13 recordsLinked to original sources
PubMed2001

Atrial fibrillation after cardiac surgery.

PURPOSE: To review the epidemiology, mechanisms, complications, predictors, prevention, and treatment of atrial fibrillation following cardiac surgery. DATA SOURCES: MEDLINE search of English-language reports published between 1966 and 2000 and a search of references of relevant papers. STUDY SELECTION: Clinical and basic research studies on atrial fibrillation after cardiac surgery. DATA EXTRACTION: Relevant clinical information was extracted from selected articles. DATA SYNTHESIS: Atrial fibrillation occurs in 10% to 65% of patients after cardiac surgery, usually on the second or third postoperative day. Postoperative atrial fibrillation is associated with increased morbidity and mortality and longer, more expensive hospital stays. Prophylactic use of beta-adrenergic blockers reduces the incidence of postoperative atrial fibrillation and should be administered before and after cardiac surgery to all patients without contraindication. Prophylactic amiodarone and atrial overdrive pacing should be considered in patients at high risk for postoperative atrial fibrillation (for example, patients with previous atrial fibrillation or mitral valve surgery). For patients who develop atrial fibrillation after cardiac surgery, a strategy of rhythm management or rate management should be selected. For patients who are hemodynamically unstable or highly symptomatic or who have a contraindication to anticoagulation, rhythm management with electrical cardioversion, amiodarone, or both is preferred. Treatment of the remaining patients should focus on rate control because most will spontaneously revert to sinus rhythm within 6 weeks after discharge. All patients with atrial fibrillation persisting for more than 24 to 48 hours and without contraindication should receive anticoagulation. CONCLUSIONS: Atrial fibrillation frequently complicates cardiac surgery. Many cases can be prevented with appropriate prophylactic therapy. A strategy of rhythm management for symptomatic patients and rate management for all other patients usually results in reversion to sinus rhythm within 6 weeks of discharge.

Adrenergic beta-Antagonists↗
PubMed2001

Recalls and safety alerts involving pacemakers and implantable cardioverter-defibrillator generators.

CONTEXT: Unanticipated pacemaker and implantable cardioverter-defibrillator (ICD) generator malfunctions sometimes warrant recall by the US Food and Drug Administration (FDA). Despite increasingly frequent device implantation, pacemaker and ICD recalls and safety alerts (advisories) remain poorly characterized. OBJECTIVES: To determine pacemaker and ICD generator advisory rates in the United States, to identify trends in these rates, and to examine their clinical and financial implications. DESIGN AND SETTING: Analysis of weekly FDA Enforcement Reports issued between January 1990 and December 2000 to identify all advisories involving pacemaker or ICD generators in the United States. Recalls and safety alerts involving lead malfunctions were not included. MAIN OUTCOME MEASURES: Number of pacemakers and ICD generators in the United States subject to FDA recall or safety alert in 1990-2000; annual pacemaker and ICD advisory rates in the United States in 1990-2000; and estimated cost of device advisories. RESULTS: During the study period, 52 advisories (median [25th and 75th percentiles], 4 [4 and 7] per year) involving 408 500 pacemakers and 114 645 ICDs (523 145 total devices) were issued. Hardware malfunctions (35 advisories affecting 280 641 devices) and computer errors (10 advisories affecting 216 533 devices) accounted for 95% of device recalls. Implantable cardioverter-defibrillators were recalled more frequently than pacemakers (mean [SD], 16.4 [1.6] vs 6.7 [0.8] advisories per 100 person-years; P<.001). Between 1995 and 2000, the annual advisory rate increased for both pacemakers (P for trend <.001) and ICDs (P for trend =.02). An estimated 1.3 million device checks and analyses and 36 187 device replacements resulted from the advisories and cost approximately $870 million. CONCLUSIONS: Pacemaker and ICD recalls and safety alerts occur frequently, affect many patients, and appear to be increasing in number and rate. With the growing number of device implants and expanding indications for device therapy, the number of patients affected by device advisories will likely continue to increase.

Defibrillators, Implantable↗
PubMed2001

Catheter ablation in patients with multiple and unstable ventricular tachycardias after myocardial infarction: short ablation lines guided by reentry circuit isthmuses and sinus rhythm mapping.

BACKGROUND: Extensive lines of radiofrequency (RF) lesions through infarct (MI) can ablate multiple and unstable ventricular tachycardias (VTs). Methods for guiding ablation that minimize unnecessary RF applications are needed. This study assesses the feasibility of guiding RF line placement by mapping to identify a reentry circuit isthmus. METHODS AND RESULTS: Catheter mapping and ablation were performed in 40 patients (MI location: inferior, 28; anterior, 7; and both, 5) with an electroanatomic mapping system to measure the infarct region and ablation lines. The initial line was placed in the MI region either through a circuit isthmus identified from entrainment mapping or a target identified from pace mapping. A total of 143 VTs (42 stable, 101 unstable) were induced. An isthmus was identified in 25 patients (63%; 5 with only stable VTs, 5 with only unstable VTs, and 15 with both VTs). Inducible VTs were abolished or modified in 100% of patients when the RF line included an isthmus compared with 53% when RF had to be guided by pace mapping (P=0.0002); those with an isthmus identified received shorter ablation lines (4.9+/-2.4 versus 7.4+/-4.3 cm total length, P=0.02). During follow-up, spontaneous VT decreased markedly regardless of whether an isthmus was identified. VT stability and number of morphologies did not influence outcome. CONCLUSIONS: A 4- to 5-cm line of RF lesions abolishes all inducible VTs in more than 50% of patients. Less ablation is required if a reentry circuit isthmus is identified even when multiple and unstable VTs are present.

Aged↗
PubMed2001

Saline-cooled versus standard radiofrequency catheter ablation for infarct-related ventricular tachycardias.

BACKGROUND: Saline cooling of the electrode during radiofrequency (RF) ablation increases lesion size in animal models. If cooled RF also increases lesion size in human infarcts, it should facilitate the termination of ventricular tachycardia (VT). METHODS AND RESULTS: In 66 patients with VT due to prior infarction, 366 ablation sites, which were classified by entrainment and isolated potentials followed by ablation during VT with either standard RF energy (247 sites) or cooled RF (119 sites), were retrospectively reviewed to compare the efficacy for terminating VT. RF energy was applied at 259 isthmus sites, 62 bystander sites, 28 inner loop sites, and 17 outer loop sites. Compared with standard RF, cooled RF terminated VT more frequently at isthmus sites where an isolated potential was present (89% versus 54%, P=0.003), isthmus sites without an isolated potential (36% versus 21%, P=0.04), and at inner loop sites (60% versus 22%, P=0.04). Termination rates were similarly low for cooled and standard RF at bystander sites (14% versus 9%, P=0.56) and outer loop sites (13% versus 11%, P=0.93). CONCLUSIONS: Greater efficacy of cooled RF for terminating VT is consistent with the production of a larger lesion in human infarctions, which should facilitate successful ablation.

Aged↗
PubMed2001

The N + 1 difference: a new measure for entrainment mapping.

OBJECTIVES: The purpose of this study was to develop and test a new entrainment mapping measurement, the N + 1 difference. BACKGROUND: Entrainment mapping is useful for identifying re-entry circuit sites but is often limited by difficulty in assessing: 1) changes in QRS complexes or P-waves that indicate fusion, and 2) the postpacing interval (PPI) recorded directly from the stimulation site. METHODS: In computer simulations of re-entry circuits, the interval from a stimulus that reset tachycardia to a timing reference during the second beat after the stimulus was compared with the timing of local activation at the site during tachycardia to define an interval designated the N + 1 difference. The N + 1 difference was compared with the PPI-tachycardia cycle length (TCL) difference in simulations and at 65 sites in 10 consecutive patients with ventricular tachycardia (VT) after myocardial infarction and at 45 sites in 10 consecutive patients with atrial flutter. RESULTS: In simulations, the N + 1 difference was equal to the PPI-TCL difference. During mapping of VT and atrial flutter, the N + 1 difference correlated well with the PPI-TCL difference (r > or = 0.91, p < 0.0001), identifying re-entry circuit sites with sensitivity of > or = 86% and specificity of > or = 90%. Accuracy was similar using either the surface electrocardiogram or an intracardiac electrogram (Eg) as the timing reference. CONCLUSIONS: The N + 1 difference allows entrainment mapping to be used to identify re-entry circuit sites when it is difficult to evaluate Egs at the mapping site or fusion in the surface electrocardiogram.

Aged↗
PubMed2000

Identification of left atrial origin of ectopic tachycardia during right atrial mapping: analysis of double potentials at the posteromedial right atrium.

INTRODUCTION: The high posteromedial right atrium is adjacent to the left atrium near the right superior pulmonary vein. We hypothesized that analysis of electrograms at this site could distinguish left from right atrial tachycardia. METHODS AND RESULTS: Atrial mapping was performed in 16 patients with left atrial origin ectopic tachycardia (11 patients with right superior pulmonary vein origin and 5 patients with other left atrial tachycardias). During left atrial tachycardia, earliest right atrial activation was recorded at the high posterior right atrium in 14 of 16 patients. At all of these 14 early sites, double potentials were recorded during tachycardia. The first potential was a far-field signal from left atrium as indicated by the following: (1) during sinus beats, the timing of the two potentials reversed such that the left atrial one was late; (2) ablation at the right atrial site did not decrease the amplitude of the first potential, but did decrease the amplitude of the second potential; and (3) the timing of activation at the adjacent left atrium agreed with that of the first potential. In the 11 right superior pulmonary vein tachycardias, the first potential was markedly earlier than the p wave onset, but in left atrial tachycardias with other origins it was later. In a control group of six patients with pacing to simulate right atrial tachycardia, double potentials were recorded in the posterior right atrium, but the timing of components did not reverse during sinus rhythm. CONCLUSION: For some left atrial ectopic tachycardias, particularly those originating from the right superior pulmonary vein, recognition of left versus right atrial origin can be accomplished during right atrial mapping by analysis of double potentials in the posteromedial right atrium.

Adult↗
PubMed2000

Mapping and radiofrequency catheter ablation of the three types of sustained monomorphic ventricular tachycardia in nonischemic heart disease.

INTRODUCTION: Sustained monomorphic ventricular tachycardia (VT) associated with nonischemic cardiomyopathy (CMP) is uncommon. Optimal approaches to catheter mapping and ablation are not well characterized, but they are likely to depend on the VT mechanism. The purpose of this study was to evaluate the mechanisms of sustained monomorphic VT encountered in nonischemic CMP and to assess the feasibility, safety, and efficacy of catheter radiofrequency ablation for treatment. METHODS AND RESULTS: Twenty-six consecutive patients with nonischemic CMP referred for management of recurrent VT were studied. In 16 (62%) patients, VT was related to a region of abnormal electrograms consistent with scar and the response to pacing suggested a reentrant mechanism. In 5 (19%) patients, VT was due to bundle branch or interfascicular reentry. In 7 (27%) patients, the VT mechanism was focal automaticity, 4 of whom had evidence of tachycardia-induced CMP. After catheter ablation targeting parts of reentrant circuits, VT was not inducible in 8 (53%) of 15 patients with scar-related reentry, was modified in 5 (33%) patients, and still was inducible in 2 (13%) patients. Ablation was successful in 5 of 5 patients with bundle branch reentry and in 6 of 7 patients with a focal automaticity mechanism. Overall, catheter ablation abolished clinical recurrence of VT in 20 (77%) of 26 patients during a follow-up of 15 +/- 12 months. CONCLUSION: Three different mechanisms of VT are encountered in patients with nonischemic CMP. The mapping and ablation approach varies with the type of VT. In this selected population, the overall efficacy was 77%.

Adolescent↗
PubMed1998

Propafenone for the treatment of supraventricular tachycardia and atrial fibrillation: a meta-analysis.

The purpose of this study was to determine propafenone's effectiveness in terminating and suppressing supraventricular arrhythmias using meta-analytic techniques. Published abstracts and manuscripts with these goals were selected and data abstracted on conversion and maintenance of sinus rhythm. Data were pooled using standard meta-analytic techniques and analyzed according to observation times, trial design (randomized versus nonrandomized), and route of drug administration. Propafenone successfully terminated 83.8% (95% confidence interval 78.1-89.7%) of supraventricular tachycardias. For supraventricular tachycardias, the proportion of patients remaining in sinus rhythm without recurrent arrhythmia was 64.6% (58.1-71.1%) at 1 year. The likelihood of converting a paroxysm of atrial fibrillation (AF) increased over time, with 76.1% (72.8-79.4%) of patients in sinus rhythm 24 hours after initiation of therapy. Patients receiving intravenous therapy were more likely to convert to sinus rhythm in the first 4 hours after drug administration. The treatment benefit of propafenone versus placebo in converting sinus rhythm was greatest in the first 8 hours after treatment (treatment benefit of 31.5% [24.5-38.5%] at 4 hours and 32.9% [24.3-41.5%] at 8 hours, p <0.01). This treatment benefit decreased to 1 1.0% (-0.6-22.4%) after 24 hours. Propafenone was effective in suppressing recurrences of AF in 55.4% (51.3-59.7%) at 6 months and 56.8% (52.3-61.3%) at 12 months. Thus, propafenone is effective in terminating supraventricular tachycardias and AF in the vast majority of patients. Suppression of arrhythmia recurrences is feasible in most patients, although its effectiveness decreases over time.

Anti-Arrhythmia Agents↗
PubMed1998

Left ventricular pseudoaneurysm after epicardial patch electrode placement.

There are many known complications of implantable cardioverter-defibrillator placement. We treated a patient in whom a left ventricular pseudoaneurysm developed secondary to epicardial patch electrode placement and cardioverter-defibrillator implantation. The presenting symptoms, diagnostic evaluation, and surgical repair are described.

Aged↗
PubMed1997

Risk of initiating antiarrhythmic drug therapy for atrial fibrillation in patients admitted to a university hospital.

BACKGROUND: The risks of antiarrhythmic therapy are increasingly recognized, but the risks associated with the initiation of antiarrhythmic therapy in patients hospitalized for atrial fibrillation are poorly defined. OBJECTIVE: To determine the incidence, time course, and predictors of adverse cardiac events that require intervention during initiation of antiarrhythmic drug therapy for atrial fibrillation. DESIGN: Retrospective chart review. SETTING: University hospital. PARTICIPANTS: 417 consecutive patients who underwent a total of 597 drug trials during a total of 550 hospitalizations for atrial fibrillation. INTERVENTION: Initiation of therapy with antiarrhythmic drugs: procainamide (189 trials), quinidine (179 trials), disopyramide (20 trials), propafenone (110 trials), flecainide (2 trials), sotalol (72 trials), and amiodarone (25 trials). Electrical conversion was performed during 247 trials. MEASUREMENTS: Incidence of adverse events and daily hazard rate were measured. Logistic regression was done to identify risk factors. RESULTS: During the 597 drug trials, 80 (13.4%) cardiac adverse events occurred in 73 patients. The risk was greatest during the first 24 hours of therapy. Bradyarrhythmias were the most common adverse event, occurring in 47 trials (7.9%); prolongation of the QT interval warranting discontinuation of drug therapy (9 trials; 1.5%) and ventricular arrhythmias (8 trials; 1.3%) were less frequent. In multivariate analysis, previous myocardial infarction was associated with increased risk (odds ratio, 1.90 [95% CI, 1.05 to 3.43]) and the association between older age and increased risk (odds ratio, 1.29 per decade [CI, 0.97 to 1.72]) was of borderline statistical significance. CONCLUSIONS: A significant risk for cardiac adverse events exists during initiation of antiarrhythmic therapy in patients hospitalized for atrial fibrillation. Observation with electrocardiographic monitoring seems advisable for 24 to 48 hours during initiation of antiarrhythmic therapy, particularly for elderly patients and patients who have previously had myocardial infarction.

Adult↗