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D L Packer

Publications and source records attributed to D L Packer.

67 records · Page 4Linked to original sources
PubMed1987

Wolff-Parkinson-White syndrome and sudden cardiac death.

Every year, individuals with no history of heart disease succumb to sudden cardiac death (SCD). Pathologic examination of the hearts usually reveals various forms of heart disease as hypertrophic cardiomyopathy or coronary artery disease. In other cases, however, there is no obvious structural heart disease, and it is possible that some of these individuals died because of a cardiac arrhythmia involving an accessory pathway. If this were the case, the most likely scenario would be onset of atrioventricular reciprocating tachycardia (AVRT), degeneration of the AVRT into atrial fibrillation with a rapid ventricular response over the accessory pathway, and subsequent death caused by the development of ventricular fibrillation. Although these events have been documented, albeit rarely, during intracardiac electrophysiologic studies, in reality very little is known about the natural history of asymptomatic and untreated patients with Wolff-Parkinson-White (WPW) syndrome. In fact, SCD in a previously asymptomatic patient with WPW syndrome is probably relatively rare. Whether asymptomatic WPW patients should undergo electrophysiologic or pharmacologic testing to determine their 'potential' to develop serious cardiac arrhythmias is controversial. The present paucity of data concerning the natural history of WPW syndrome in asymptomatic patients militates against successful identification of those patients who are at risk for sudden death. Long-term prospective studies are necessary to clarify which asymptomatic patients with WPW syndrome require treatment.

Death, Sudden↗
PubMed1986

Tachycardia-induced cardiomyopathy: a reversible form of left ventricular dysfunction.

Eight patients, aged 5 to 57 years, with uncontrolled symptomatic tachycardia for 2.5 to 41 years (mean 15) and significant left ventricular (LV) dysfunction in the absence of any other apparent underlying cardiac disease underwent evaluation. Incessant tachycardia was present for 0.5 to 6.0 years (mean 2.1) in 7 patients. One patient had an ectopic atrial tachycardia and 7 patients had an accessory atrioventricular pathway that participated in reciprocating tachycardia. Six patients underwent surgery; the ectopic focus was ablated in 1 patient and an accessory pathway was divided in 5 patients. One patient underwent open ablation of the His bundle and 1 patient underwent closed-chest ablation of the atrioventricular conduction system. Myocardial biopsy specimens were obtained from 5 patients, none of which yielded a specific diagnosis. Pretreatment radionuclide angiography demonstrated a mean ejection fraction (EF) of 19 +/- 9% (range 10 to 35%). Following tachycardia control a marked improvement in LV function was noted in 6 of 8 patients at rest and in 1 additional patient during exercise. The EF increased to 33 +/- 17% (range 16 to 56%) an average of 8 days after treatment and to 45 +/- 15% (range 22 to 67%) at late follow-up 3.5 +/- 40 months (mean 17) later (p less than 0.005). Seven patients remain asymptomatic 11 to 40 months (mean 22) after the corrective procedure and have resumed normal activities. These findings suggest that chronic uncontrolled tachycardia may result in significant LV dysfunction, which is reversible in some cases after control of the arrhythmia.

Adolescent↗
PubMed1985

Cardiac involvement in myotonic muscular dystrophy.

Cardiac illness in myotonic muscular dystrophy (MyD) is infrequent, but subclinical cardiac involvement in MyD is very common (found in 42 of 46 subjects) and may be responsible for sudden death. In this series, we found ECG abnormalities in 72%, left ventricular dysfunction in 70%, mitral valve prolapse in 37%, and sudden death in 4%. Four deaths during the study period were due to acute left ventricular failure, one to sepsis and respiratory insufficiency, and one was unexplained. We did not find ominous bradyarrhythmias or atrioventricular block, evidence of congestive heart failure, noninvasive evidence of coronary artery disease, or any correlation of type or amount of cardiac involvement with any clinical parameter such as age, sex, or severity of systemic dystrophy. We feel tachyarrhythmias may play as important a role in sudden death of myotonic muscular dystrophy subjects as bradyarrhythmias, and coronary artery disease in addition to cardiac dystrophy may produce arrhythmias and myocardial dysfunction in myotonic muscular dystrophy. In addition, some subjects have an unusual form of resting left ventricular dysfunction which improves with exercise. The most important problem in the clinical management of myotonic muscular dystrophy subjects is sudden death, and the solution does not appear to be empiric ventricular pacing. Our recommendations for prophylaxis of sudden death in myotonic muscular dystrophy are noninvasive investigation of coronary artery disease in subjects with significant risk factors, with angiography and surgery if indicated: detailed evaluation of syncopal and presyncopal events, including electrophysiologic testing, with pacemaker or antiarrhythmic drug therapy if indicated; and consideration of ventricular pacing of asymptomatic subjects if severe bradycardia or marked intraventricular conduction delay develops during follow-up, serial 12-lead ECGs. The documentation of tachyarrhythmias during sudden death and syncopal episodes in myotonic muscular dystrophy subjects makes ventricular pacing alone an uncertain modality for prevention of sudden death in subjects with only mildly lengthened PR or QRS intervals, and suggests a combination of pacemaker and antiarrhythmic drug therapy for the myotonic muscular dystrophy subject with syncope of no apparent cause.

Adult↗
PubMed1985

Right ventricular isolation procedures for nonischemic ventricular tachycardia.

Nonischemic ventricular tachycardia most commonly arises in the right ventricular free wall and is frequently refractory to medical therapy. Many different types of surgical procedures have been employed to treat medically refractory nonischemic ventricular tachycardia arising in the right ventricle, but the results of these procedures have been less than optimal. The majority of these surgical procedures have been directed toward ablation of the site (or sites) of origin of the tachyarrhythmia and have failed because of the frequent occurrence of multifocal or polymorphic ventricular tachycardia in these patients. We first employed localized surgical isolation procedures to control nonischemic ventricular tachycardia arising in the right ventricular free wall in 1979. These localized procedures evolved into the development of a technique for isolating the entire right ventricular free wall from the remainder of the heart to control ventricular tachyarrhythmias arising from multiple sites in the right ventricle. Case histories are reported of two patients who underwent localized isolation procedures in 1979 as well as two patients who underwent total disconnection of the right ventricle in 1982. The follow-up period in these four patients ranges from 2 to 5 years and the control of their tachyarrhythmias has been uniformly successful. However, surgical isolation of the entire right ventricular free wall has resulted in progressive dilatation of the right ventricle as documented by serial echocardiography. The pathophysiology of the progressive right ventricular dilatation postoperatively is discussed in terms of etiology and prevention, and the indications for application of localized and total isolation procedures for nonischemic right ventricular tachycardia are outlined.

Adolescent↗
PubMed1984

Surface electrocardiographic clues suggesting presence of a nodofascicular Mahaim fiber.

Standard electrocardiograms from 87 consecutive patients with tachycardia of left bundle branch block configuration were analyzed retrospectively for features that might be characteristic of tachycardia utilizing a nodofascicular Mahaim fiber. The study group consisted of 13 patients with nodofascicular tachycardia, 34 with supraventricular tachycardia and aberrant conduction over the His-Purkinje system, 22 with ventricular tachycardia and 18 with antidromic tachycardia utilizing a right-sided accessory atrioventricular pathway. Six variables present during tachycardia of left bundle branch block configuration were predictive of a nodofascicular fiber: cycle length between 220 and 450 ms, QRS axis of 0 to -75 degrees, QRS duration 0.15 second or less, R wave in lead I, rS wave in precordial lead V1 and a precordial transition from a negative to a positive QRS complex after lead V4. All six criteria were present in 16 of the 87 patients. No patient with ventricular tachycardia satisfied these criteria, whereas 3 of 34 with supraventricular tachycardia, 1 of 18 with antidromic tachycardia and 12 of 13 with tachycardia using a nodofascicular fiber did. It is concluded that analysis of the surface electrocardiogram during tachycardia may suggest the presence of a nodofascicular fiber.

Adolescent↗
PubMed1984

Utility of electrophysiologic studies in the management of tachycardia, sudden death, and syncope.

The demonstrable value of EP studies for any given diagnostic or therapeutic category, in the last analysis, is largely a function of the subjects studied. Extrapolations from published data (that generally reflect a highly select patient population) to an individual patient can be fraught with error. Considerations of sensitivity and specificity must be balanced against the important need for information in patients at risk from life-threatening arrhythmias. We must never forget, however, that the EP substrate for any arrhythmia is not, as one might wish, a "black box" that should be expected to respond in a reproducible fashion to stimulation. The substrate is dynamic and subject to modification by change in autonomic tone, stretch, blood flow, basal rate, pH, electrolytes, oxygenation, and exposure to perhaps as yet undiscovered humoral mediators. The challenge to the clinical electrophysiologist is therefore not to exaggerate his efforts in one direction (i.e. programmed stimulation) while disregarding the other variables mentioned. Nor should we be disappointed and discard this approach because our expectations of an oversimplified model of arrhythmia testing are not fulfilled. Thus, in addition to careful stratification of patients, baseline studies should perhaps be carried out with more deliberate consideration of autonomic tone (exercise, isoproterenol), stretch (volume, handgrip, afterload), stress (physical and psychological), local anesthetic used, and body position. Only in this way will the scientific basis for acute and chronic EP testing be firmly established.

Death, Sudden↗
PubMed1984

Preexcited reciprocating tachycardia in patients with Wolff-Parkinson-White syndrome: incidence and mechanisms.

During the electrophysiologic study of 435 patients referred for evaluation of Wolff-Parkinson-White syndrome, 42 (10%) had preexcited reciprocating tachycardia (defined as a macro-reentrant tachycardia that used an accessory atrioventricular [AV] pathway for antegrade conduction). The ages of the patients ranged from 9 to 67 years (27 +/- 14). Thirty-three were male patients, nine female, and eight had Ebstein's anomaly. Preexcited reciprocating tachycardia cycle length was 220 to 430 msec (294 +/- 42). Significant hemodynamic compromise in the laboratory directly related to preexcitated reciprocating tachycardia occurred in only one patient. However, in 10 patients a transformation to atrial fibrillation was seen after a spontaneously occurring premature atrial contraction. Only 17 of the 42 patients with preexcited reciprocating tachycardia during electrophysiologic study had the same tachycardia documented clinically. These 17 patients were more often younger with multiple accessory pathways and with no history of orthodromic reciprocating tachycardia when compared with 25 patients in whom preexcited reciprocating tachycardia could be induced only in the laboratory. Preexcited reciprocating tachycardia was induced in the laboratory in 22 of 374 (6%) patients with single accessory pathways and in 20 of 61 (33%) of those with multiple accessory pathways. In the 20 patients with multiple accessory pathways, the spectrum of reentrant circuits included fusion over two or more accessory pathways or fusion over both an accessory pathway and the AV node. In the 22 patients with a single accessory pathway and true antidromic reciprocating tachycardia, all but two episodes were at least 4 cm from the AV node. No patient with true antidromic reciprocating tachycardia had a posterior septal accessory AV pathway. Only in patients with multiple accessory pathways was the posterior septal accessory AV pathway used as the antegrade limb.

Adolescent↗
PubMed1983

Ventricular tachycardia induced by atrial stimulation in patients without symptomatic cardiac disease.

Ten patients with an unusual form of ventricular tachycardia (VT) are described. All were young (mean age 21 years) at the onset of VT, symptoms were of long duration (mean 7 years), none had symptomatic organic heart disease, VT was induced by atrial and ventricular stimulation, VT had a characteristic QRS morphologic picture resembling right bundle branch block with left-axis deviation and 9 had early retrograde His deflections during VT. Supraventricular tachycardia (SVT) was excluded in every patient by electrophysiologic study, although QRS morphologic characteristics and clinical stability of these patients during tachycardia frequently led to the diagnosis of SVT before referral. Four patients received verapamil during electrophysiologic testing. Verapamil slowed and terminated VT in all. Three patients are being treated chronically with oral verapamil, 3 patients with conventional antiarrhythmic agents and 1 with a radiofrequency ventricular pacemaker.

Adolescent↗