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Biomedical subjects

J M McComb

Publications and source records attributed to J M McComb.

At least 19 recordsLinked to original sources
PubMed1992

Arrhythmias after cardiac transplantation.

The etiology and clinical significance of sustained arrhythmias, and atrial and ventricular premature complexes (APCs and VPCs, respectively) after heart transplantation are controversial. Fifty adult recipients surviving > 2 weeks were studied by continuous telemetry while in the hospital and by ambulatory electrocardiographic monitoring at 2, 4, 6, 12 and 24 weeks after transplantation. The median APC frequency was greater among subjects who experienced allograft rejection in the early postoperative period (0.7/hour, range 0 to 23) than among those who did not (0.2/hour, range 0 to 10.4) (p = 0.04). The APC frequency in all subjects decreased from 0.25/hour (range 0 to 23) early to 0/hour (0 to 14) later (p = 0.04). Atrial flutter was the most frequent sustained arrhythmia; it was recorded in 5 of 21 rejectors and in 1 of 29 nonrejectors (p = 0.04), and 11 of 16 episodes (69%) were related to acute rejection temporally. VPCs were recorded in all patients early after transplantation, but the median frequency subsequently decreased from 4.6/hour (range 0.5 to 470) early to 1.25/hour (range 0 to 225) later (p < 0.001). VPC frequency was unrelated to rejection. Sustained ventricular tachycardia was recorded once and was caused by the proarrhythmic effect of flecainide. Thus, APCs and VPCs occur frequently after transplantation. Frequent APCs are associated with rejection, whereas the main determinant of VPC frequency is time after transplantation. Atrial flutter is closely associated with rejection and should be regarded as an indication for endomyocardial biopsy. Ventricular tachycardia occurs seldom, and in this study was due to proarrhythmic drug effects.

Adult↗
PubMed1992

The management and outcome of late post-infarct ventricular tachycardia presenting to a district general hospital.

A review was undertaken of late post-infarct ventricular tachycardia in a district hospital cardiac care unit in order to study the clinical course of a total population of such patients from initial presentation to ultimate outcome. Thirty-six patients with this diagnosis were identified over a 3 1/2-yr period. Twelve were treated by empirically chosen antiarrhythmic drugs. Twenty-four were referred for electrophysiologically guided treatment, of whom 16 were treated by antiarrhythmic drugs, 3 by anti-ischaemic measures alone, and 5 by non-pharmacological antiarrhythmic treatments (antiarrhythmic surgery, percutaneous ablation, defibrillator implantation, cardiac transplantation). Of those treated empirically, 4 died in hospital of their arrhythmia, 1 died suddenly at home, and 2 suffered non-fatal arrhythmia recurrences during mean follow-up of 20 months. There were no arrhythmic deaths in those whose treatment was guided by serial electrophysiology studies, although 4 patients died of cardiac failure or reinfarction, and 3 were hospitalised with a recurrence of ventricular tachycardia during mean follow-up of 16 months. Age, concomitant medical problems and the apparent response to initial antiarrhythmic therapy were the main factors influencing management decisions. The apparent superiority of more intensive management strategies based on electrophysiology studies must be interpreted in the context of the selection processes applied to the total population initially presenting.

Aged↗
PubMed1992

Surgery for ventricular tachycardia associated with right ventricular dysplasia: disarticulation of right ventricle in 9 of 10 cases.

Ten patients (nine men, one woman; mean age 39 years) with arrhythmogenic right ventricular dysplasia underwent surgery to control life-threatening drug refractory ventricular arrhythmias. All had ventricular tachycardia causing syncope and six had a history of cardiac arrest. In all a minimum of three antiarrhythmic drugs (mean five) had been ineffective. At operation, the right ventricle was grossly diseased in all patients. Ventricular tachycardias were induced and mapped intraoperatively in all patients. The surgical plan was to ablate the arrhythmogenic focus if it was less than 4 cm2; one patient was so managed. Of the remaining nine, four underwent partial (approximately 40% of the right ventricular free wall) and five underwent total right ventricular disarticulation. All survived the operation and are alive at a mean follow-up interval of 24 months (range 5 to 67). Two patients developed new sustained ventricular tachycardias. These were well tolerated and, unlike the original arrhythmias, were easily controlled by drug treatment. All patients who underwent right ventricular disarticulation manifested signs of right heart failure in the early postoperative period, but these lessened progressively with the development of systolic septal movement into the right ventricular cavity. All 10 patients are in New York Heart Association class I or II at last review. In selected patients with arrhythmogenic right ventricular dysplasia, surgery offers a curative treatment for ventricular tachycardia and should be considered for patients whose arrhythmias are life-threatening and refractory to drug treatment.

Adolescent↗
PubMed1992

QT dispersion in sinus beats and ventricular extrasystoles in normal hearts.

OBJECTIVE: Recent studies have suggested that QT interlead variability (dispersion) on the surface electrocardiogram may have potential as a measure of recovery time dispersion. To test this hypothesis further QT dispersion occurring in sinus beats was compared with that in ventricular extrasystoles. DESIGN: Simultaneous electrocardiograms were recorded at 50 mm/s during sinus rhythm in a drug free state while ventricular extrastimuli were introduced by programmed right ventricular stimulation at different coupling intervals. QT dispersion, defined as the difference between the maximum and minimum QT, was calculated separately for the extrasystoles and preceding and following sinus complexes. To correct for the influence of the number of measurable leads on QT dispersion, an "adjusted" QT dispersion calculated as QT dispersion/square root of the number of measurable leads, was used to compare sinus complexes and extrasystoles. PATIENTS: Nine patients were studied who were undergoing electrophysiological study for investigation of palpitation and were found to have electrically normal ventricles. RESULTS: At all coupling intervals tested "adjusted" QT dispersion was significantly greater in the ventricular extrasystoles than in either the preceding or following sinus complexes. For the coupling interval 350 ms, the 95% confidence intervals for the difference between means was 52 to 78 ms (preceding sinus complex) and 56 to 82 ms (following sinus complex) (p less than 0.00001). There was no correlation between the coupling interval and the magnitude of the "adjusted" QT dispersion. CONCLUSION: These results accord fully with expected differences in ventricular recovery time dispersion and offer further support for the hypothesis that QT dispersion reflects regional variation in ventricular recovery. If substantiated by invasive studies, these findings have wide implications for both the usefulness and the method of QT measurement.

Cardiac Complexes, Premature↗
PubMed1992

Incessant atrial tachycardia accelerated by pregnancy.

A 24 year old patient presented with incessant atrial tachycardia during the course of a twin pregnancy. Medical treatment slowed the ventricular response without restoring sinus rhythm. During labour the tachycardia spontaneously reverted to sinus rhythm. Subsequently the same arrhythmia was documented with a slower ventricular response than during pregnancy.

Adult↗
PubMed1991

Reduction in QT dispersion by sotalol following myocardial infarction.

Increased dispersion of ventricular recovery time is believed to be a substrate for serious ventricular arrhythmias. Class III antiarrhythmic drugs probably operate by decreasing dispersion through homogeneous prolongation of recovery time. A single surface QT value gives no information on recovery time dispersion but interlead variation in QT may be relevant. QTc dispersion was measured in 67 patients post myocardial infarction randomized to treatment with either sotalol or placebo. QTc dispersion was calculated as the difference between the maximum and minimum QTc in any surface electrocardiogram lead. Both maximum QTc and QTc dispersion varied considerably following infarction but throughout the 6-month follow-up period maximum QTc was significantly greater (P less than 0.05) and QTc dispersion significantly less (P less than 0.05) in patients on sotalol compared with placebo. These findings are in accord with expected changes in ventricular recovery time and provide strong support for the hypothesis that surface electrocardiogram QT variation reflects regional differences in ventricular recovery time.

Arrhythmias, Cardiac↗
PubMed1991

Electrophysiologic effects and antiarrhythmic efficacy of recainam in patients with supraventricular tachycardia.

Recainam is a new antiarrhythmic agent with class Ic properties. To evaluate its electrophysiologic effects and antiarrhythmic efficacy in patients with recurrent supraventricular tachycardia (SVT), programmed electrical stimulation was performed in 10 patients before and after intravenous recainam (loading dose 0.8 mg/kg, infusion 1 mg/kg/h), and in four patients on oral recainam 1,200 mg/day. Five patients had atrioventricular (AV) node reentrant tachycardia; five had AV-reciprocating tachycardia. There were no significant changes in electrocardiographic and intracardiac intervals after either intravenous or oral recainam. After intravenous recainam, the ventricular effective refractory period (ERP) shortened (231 +/- 14-219 +/- 9 ms, p less than 0.05). The antegrade ERP of all three bidirectional accessory pathway markedly prolonged, but the effect on retrograde accessory pathway and AV node ERPs was unremarkable. SVT induction was prevented in three of 10 patients and SVT cycle length increased modestly in seven (357 +/- 44-374 +/- 42 ms, p = 0.07). On oral recainam, an increase in the frequency of spontaneous SVT occurred in two patients. At the doses given, recainam caused less electrophysiologic change than expected, had modest antiarrhythmic efficacy, and might have significant arrhythmogenic potential.

Administration, Oral↗
PubMed1991

Long-term pacing in heart transplant recipients is usually unnecessary.

The indications for and timing of permanent pacing were reviewed in all 17 of 154 adult heart transplant recipients at this center who have had permanent pacemakers implanted. Resting 12-lead ECGs recorded during routine follow-up were examined. A prospective study of pacing requirement was then undertaken. Holter monitoring was performed before and after reprogramming the pacemakers to VVI mode at 50 beats/min. Exercise responses in various pacing modes were then assessed in seven patients with rate responsive pacemakers using a standard Bruce protocol treadmill test. The indication for pacing was sinus node dysfunction in 59% (10/17) and atrioventricular (AV) block in 41% (7/17). The majority of pacemakers were implanted between seven and 21 days after transplantation. There was a progressive reduction in the frequency of pacing on 12-lead ECGs with time after transplantation. There was a progressive reduction in the frequency of pacing on 12-lead ECGs with time after transplantation. Eight of 14 patients with empirically selected programming paced during Holter monitoring. After reprogramming to 50 beats/min VVI mode only three of 14 patients, all with sinus node dysfunction, paced. Rate responsive pacing made no difference to exercise time. The requirement for long-term pacing in cardiac transplant recipients is small (3/154) and is limited to patients with sinus node dysfunction. Rate responsive pacing did not increase exercise tolerance.

Adult↗
PubMed1991

Acute and chronic hemodynamic impact of total right ventricular disarticulation.

Right ventricular disarticulation is a radical operation to control ventricular arrhythmias in patients with arrhythmogenic right ventricular dysplasia. This report describes the acute and chronic hemodynamic impact of the procedure based on our experience of five patients with life-threatening arrhythmias unresponsive to medical therapy who have undergone total disarticulation of the right ventricle. Although all patients suffered acute postoperative hemodynamic problems, all survived and returned to an excellent functional class. Right ventricular disarticulation should be considered in patients with drug refractory ventricular tachycardias due to arrhythmogenic right ventricular dysplasia when the arrhythmia either poses a life threat or results in chronic morbidity.

Adult↗
PubMed1990

Propafenone.

Explore the source record for details and available documents.

Adult↗
PubMed1990

Surgery for control of recurrent life-threatening ventricular tachyarrhythmias within 2 months of myocardial infarction.

Twenty-seven patients (mean age 57 +/- 7 years) underwent surgery for control of recurrent drug-refractory ventricular tachyarrhythmias (uniform ventricular tachycardia alone in 9 patients, ventricular tachycardia and ventricular fibrillation in 15 and ventricular fibrillation alone in 3) within 2 months of acute myocardial infarction. The mean number of major arrhythmic episodes per patient was 15 (range 2 to 200) and of drug failures 4 +/- 2. Left ventricular function was severely impaired in the majority (ejection fraction 29%; range 14% to 47%) and 18 patients (66%) had a left ventricular aneurysm. Endocardial resection guided by a combination of endocardial activation mapping during tachycardia and fragmentation mapping during sinus rhythm was performed in all patients. All electrically abnormal left ventricular endocardium was excised. Eight patients (29.6%) died within 30 days of surgery. Death was not related to age, time of surgery after infarction, ventricular function, bypass time or type of arrhythmia. Patients requiring emergency surgery had a higher early postoperative mortality rate than did those undergoing planned surgery (43% versus 15%). During a follow-up period of 32 +/- 20 months, there have been no arrhythmic deaths and only three patients (16%) have required antiarrhythmic drug therapy. When required in the early weeks after infarction, surgery for ventricular arrhythmias offers a high cure rate at a risk related to the patient's preoperative arrhythmia frequency, which in turn relates to the risk of arrhythmic death.

Adult↗
PubMed1990

Atrial antitachycardia pacing in patients with supraventricular tachycardia: clinical experience with the Intertach pacemaker.

During a 3-year period, 22 patients with recurrent supraventricular tachycardia have been treated with antitachycardia pacemakers (Intermedics Intertach, 262-12, n = 17, and Intertach II, 262-16, n = 5). Eighty-two percent were female, the mean age was 44 +/- 14 years; 86% had atrioventricular node reentrant tachycardia. Symptoms had occurred over 11.8 +/- 7.1 years, with 3.6 hospital admissions per patient, despite 4.7 +/- 2.1 antiarrhythmic drugs. Following pacemaker implantation, during a follow-up of 14.8 +/- 11.5 months, only two patients have been readmitted to a hospital because of supraventricular tachycardia (mean 0.1 per patient). One patient is taking an antiarrhythmic agent, and four are taking beta adrenergic blocking agents. Thus, 23% are taking cardioactive drugs (it was anticipated that two patients would continue on drugs after pacemaker implantation). There have been no serious complications. Atrial antitachycardia is thus an effective therapy in carefully selected patients with recurrent supraventricular tachycardia, reducing hospital admissions for supraventricular tachycardia and reducing the need for antiarrhythmic drugs.

Adrenergic beta-Antagonists↗
PubMed1990

QT dispersion: an indication of arrhythmia risk in patients with long QT intervals.

Homogeneity of recovery time protects against arrhythmias whereas dispersion of recovery time is arrhythmogenic. A single surface electrocardiographic QT interval gives no information on recovery time dispersion but the difference between the maximum and minimum body surface QT interval may be relevant. This hypothesis was tested by measuring the dispersion of the corrected QT interval (QTc) in 10 patients with an arrhythmogenic long QT interval (Romano Ward and Jervell and Lange-Nielsen syndromes or drug arrhythmogenicity) and in 14 patients without arrhythmias in whom the QT interval was prolonged by sotalol. QTc dispersion was significantly greater in the arrhythmogenic QT group than in the sotalol QT group. In patients with prolonged QT intervals, QT dispersion distinguished between those with ventricular arrhythmias and those without. This supports the hypothesis that QT dispersion reflects spatial differences in myocardial recovery time. QT dispersion may be useful in the assessment of both arrhythmia risk and the efficacy of antiarrhythmic drugs.

Adolescent↗
PubMed1989

Surgery for ventricular tachyarrhythmias based on fragmentation mapping in sinus rhythm alone.

Intraoperative arrhythmia activation mapping underlies the impressive success of surgery for sustained uniform ventricular tachycardia. Unstable arrhythmias and those intraoperatively noninducible, however, are not amenable to activation mapping and strategies for dealing with them are poorly defined. We propose that fragmentation mapping in sinus rhythm can be used to direct surgery in such situation. In 21 (33%) of 64 patients operated upon at this unit, intra-operative arrhythmia mapping was impossible because of non-inducibility in 17 (27%) and unstable morphology in 4 (6%). Endocardial resection was performed in all areas showing 'fragmented' local electrograms (greater than 100 ms duration at 30-300 Hz filtering). Mean patient characteristics included: age 51 years; LV ejection fraction 32%; major arrhythmic episodes 16 (range 2-200); antiarrhythmic drug failures, 4. There were 5 (24%) early postoperative deaths (heart failure 3; sudden 1; metabolic 1) and 1 early arrhythmia recurrence. There were 3 late non-arrhythmic deaths and 1 further arrhythmia recurrence during follow-up of 23 +/- 19 months. Both patients with documented postoperative arrhythmic episodes were controlled on previously ineffective antiarrhythmic drug therapy. Fragmentation mapping in sinus rhythm successfully extends the surgical option to arrhythmias previously considered inoperable. The results compare favourably with those for arrhythmias in which surgery was directed by activation mapping.

Adolescent↗
PubMed1989

Latent functional duality in an accessory pathway.

Accessory atrioventricular pathways classically possess neither decremental conduction nor functional duality. This report details an accessory pathway in which functional longitudinal dissociation, with decremental ventriculoatrial conduction in each component, was observed after, but not before, administration of the antiarrhythmic drug recainam.

Adult↗
PubMed1989

Recurrent ventricular tachycardia associated with anomalous left coronary artery from the pulmonary artery in a child managed by revascularisation and map-guided endocardial resection.

A 13 year old girl with recurrent ventricular tachycardia that occurred in association with anomalous origin of the left coronary artery from the pulmonary artery is described. Such an arrhythmia has not been described before. Ligation of the anomalous left coronary artery led to more frequent episodes of ventricular tachycardia with evidence of myocardial ischaemia. She was successfully managed by revascularisation (to establish a two coronary system) and map-guided left ventricular aneurysmectomy.

Adolescent↗