Prolonged QRS duration (QRS >/=170 ms) and left axis deviation in the presence of left bundle branch block: A marker of poor left ventricular systolic function?

BACKGROUND: Left bundle branch block (LBBB) is commonly associated with structural heart disease and left ventricular dysfunction. We propose that the QRS duration and degree of left-axis deviation (LAD) identify significant left ventricular systolic dysfunction in patients with LBBB. METHODS: In this prospective study the ejection fraction (EF) of 300 consecutive patients with LBBB was evaluated by echocardiography. The relationship between QRS duration and LAD (axis between -30 degrees and -90 degrees ) and EF were derived. RESULTS: There was no significant difference in age, sex, presence of ischemic or nonischemic cardiomyopathy and valvular heart disease, and EF among the patients with or without LAD. The EF of patients with QRS >/=170 milliseconds with LAD (n = 20) and without LAD (n = 18) was 25% +/- 16% and 23% +/- 13%, respectively (P =.71). The mean EF (24% +/- 10%) of the patients with a QRS duration of >/=170 milliseconds (n = 38) was significantly lower than the mean EF (36% +/- 16%) of the patients with a QRS duration of <170 milliseconds (n = 262, P <.015). The QRS duration also had a significant (P <.001) inverse correlation with EF (R = 0.37, adjusted R (2) = 0.13, SE of estimate = 16.21). However, the QRS axis was not significantly correlated with EF and did not have added predictive value. CONCLUSIONS: The QRS duration has a significant inverse relationship with EF and prolongation of QRS duration (>/=170 milliseconds) in the presence of LBBB is a marker of significant left ventricular systolic dysfunction. The presence of LAD in LBBB does not signify a further decrease in EF.

Adolescents in the age of AIDS: myths, misconceptions, and misunderstandings regarding sexually transmitted diseases.

The purpose of this study is twofold: to evaluate the extent of knowledge possessed by young people residing in an urban sexually transmitted disease (STD) and AIDS epicenter about STDs, including AIDS; and to determine whether knowledge levels varied by age, gender, race/ ethnicity, and/or previous health instruction. A total of 867 adolescents (472 females and 395 males) attending a large public high school in New York City completed a self-administered survey. Levels of knowledge about AIDS transmission and prevention were high (mean percentage correct = 91.8%). Nonetheless, adolescent respondents locked awareness about the prevalence of common STDs, had limited understanding of the ways in which these diseases can be transmitted and prevented, and were unaware of potentially serious sequelae resulting from exposure to infectious agents (e.g., infertility from chlamydial infections). Young people who had taken a health education course in which STDs were discussed did slightly better on the knowledge survey than did their peers. While the prevention of HIV infection is, and should be, a national priority, more concerted efforts are needed to better educate young people about other STDs in the overall context of sexual health.

Syncope masquerading as a panic disorder: role of the subcutaneous loop recorder in eliciting the appropriate diagnosis.

The present case describes a 49-year-old woman with apparent panic disorder in whom the Reveal Plus, a newly developed subcutaneous loop recorder, was used to show that the panic attacks were secondary to prolonged episodes of ventricular asystole.

Asymptomatic left ventricular permanent pacemaker malposition detected on routine follow-up--a case report.

The authors present an asymptomatic left ventricular pacemaker lead malposition that was detected upon routine 2-D Echocardiography. Clinical implication diagnosis and therapeutic options on left ventricular pacemaker lead malposition are discussed.

Time dependent changes in duration of ventricular repolarization after AV node ablation: insights into the possible mechanism of postprocedural sudden death.

Although effective, there is a disturbing incidence of sudden death after AV node ablation. The mechanism may be related to proarrhythmia associated with prolongation in ventricular repolarization from the sudden decrease in heart rate. To examine this issue, we studied 15 patients undergoing complete radiofrequency ablation of the AV node for rapid atrial arrhythmias. Twelve-lead ECGs of paced rhythms at rates of 60, 80, 100, and 120 beats/min were recorded at time points of 30 minutes, 24 hours, 1 week, and 1 month after ablation. The QT interval was measured in the limb and precordial leads with the best T wave offset. The change in the QT interval (delta QT) relative to the measurement at 30-minute postablation was calculated. For comparison, a similar procedure was performed on patients receiving pacemakers for primary bradycardia (n = 5). The mean QT interval at 60 beats/min, 30-minutes postablation was significantly longer than at time points thereafter (482 +/- 39 vs 446 +/- 28 ms at 1 month, limb leads, for example, P < 0.05). Analysis of delta QT revealed a significant shortening of the QT interval at nearly every paced rate at every time point relative to the value at 30-minute postablation. The QT intervals shortened and stabilized after 24 hours. Neither the QT interval nor delta QT changed significantly in patients paced for primary bradycardia. We conclude that there is a relative increase in the duration of ventricular repolarization after AV node ablation, which then decreases and stabilizes after 24 hours. Such changes are not seen in patients being paced for primary bradycardia. This data is consistent with the hypothesis that sudden death after AV node ablation may be related to proarrhythmia from prolonged ventricular repolarization.

Effects of aging and gender on QT dispersion in an overtly healthy population.

The objective of this study was to measure the normal variation of QT dispersion (QTd) with respect to age and gender. The QT interval is a measure of the duration of ventricular depolarization and repolarization, while the QTd is a measure of the variability of the ventricular recovery time. The QTd has been suggested as a means of identifying those patients at risk for sustained ventricular tachyarrythmias and sudden cardiac death (SCD). A total of 250 patients (120 women, 130 men; age range 20-86 years) were recruited for this study. The QT intervals were measured in each of the 12 standard leads of the electrocardiogram. Data are presented as mean (mu) +/- SD. The QTd did not vary significantly within the same gender. A significant difference (P < 0.001) was noted in QTd between men (age [mu] = 53.3 +/- 15.6 years, QTd = 0.044 +/- 0.019 s) and women (age [mu] = 52.1 +/- 15.1 years, QTd = 0.034 +/- 0.015 s). Overall, men had a greater QTd, while women had a longer QT. In conclusion, we found that men had a longer QTd, which may explain the increased risk of SCD. However, women have a longer QT interval with a smaller QTd. A longer QTmin, as opposed to a longer QTmax, is responsible for the shorter QTd in women. This longer QTmin in women may predispose to an increased risk of drug induced torsades de pointes.

Double-wave reentry in orthodromic atrioventricular reciprocating tachycardia: paradoxical shortening of the tachycardia cycle length with development of ipsilateral bundle branch block.

INTRODUCTION: Attempts to terminate reentrant tachyarrhythmias by rapid pacing may accelerate the tachycardia. One mechanism for acceleration is double-wave reentry, where two simultaneous wavefronts travel around the same circuit. METHODS AND RESULTS: We report pacing acceleration of AV reciprocating tachycardia (AVRT) due to double-wave reentry in a patient with Wolff-Parkinson-White syndrome. The patient had presented with atrial fibrillation and rapid conduction across a left lateral bypass tract. Intravenous procainamide was given during electrophysiologic study because of incessant atrial fibrillation and restored sinus rhythm. Orthodromic AVRT was induced and attempts to terminate the AVRT with right ventricular pacing initiated two alternate tachycardias, both with a left bundle branch block (LBBB) morphology. The first tachycardia, as expected for bundle branch block ipsilateral to the bypass tract, had a longer cycle length (CL) than the original tachycardia (366 msec compared to 297 msec). The second tachycardia had a paradoxically shorter CL, 238 msec compared to 297 msec. Electrogram analysis revealed that the circuit traversed by the accelerated LBBB tachycardia was the same as the slower LBBB tachycardia. The activation sequence revealed two independent wavefronts, traversing this common circuit. As described previously in experimental models, double-wave reentry was initiated when an antidromic-stimulated impulse blocked before colliding with the previous orthodromic impulse, thus allowing two orthodromic impulses to circulate within the circuit. CONCLUSION: We speculate that conduction slowing by procainamide combined with the intrinsic AV nodal delay resulted in the necessary increase in the excitable gap required to develop double-wave reentry. This is the first description of sustained double-wave reentry in humans.

Rhythm management in atrial fibrillation--with a primary emphasis on pharmacologic therapy: Part 3.

Atrial fibrillation (AF) is the most common, sustained, symptomatic tachyarrhythmia that clinicians are called upon to manage. Management strategies include ventricular rate control coupled with anticoagulation, versus restoration and maintenance of sinus rhythm. Rate control may be achieved pharmacologically, with agents that impair AV nodal conduction directly and/or by increasing parasympathetic/sympathetic balance, or by modifying or ablating the AV nodal region anatomically. Rhythm control may be achieved by electrical or pharmacologic conversion followed by maintenance of sinus rhythm by pharmacologic (or occasionally ablative) therapies. This article will present current approaches to rate and rhythm control issues in atrial fibrillation. Parts 1 and 2, published previously, dealt with rate control and with the restoration of sinus rhythm. Part 3, the current article, details the selection process of choosing a therapy to maintain sinus rhythm, including the likelihood of success, the risks of therapy, and individualization of therapy as dependent upon the nature of the structural heart disease present. It also discusses nonpharmacologic approaches that have been recently developed or are undergoing development. One suggested drug selection algorithm is provided.

Rhythm management in atrial fibrillation--with a primary emphasis on pharmacological therapy: Part 2.

Atrial fibrillation (AF) is the most common, sustained, symptomatic tachyarrhythmia that clinicians are called upon to manage. Management strategies include ventricular rate control coupled with anticoagulation, versus restoration and maintenance of sinus rhythm. Rate control may be achieved pharmacologically, with agents that impair AV nodal conduction directly and/or by increasing parasympathetic/sympathetic balance, or by modifying or ablating the AV nodal region anatomically. Rhythm control may be achieved by electrical or pharmacological conversion followed by maintenance of sinus rhythm by pharmacological (or occasionally ablative) therapies. This article will present current approaches to rate and rhythm control issues in AF. Part 1, published previously, dealt with rate control. Part 2, the current article, details approaches to the restoration of sinus rhythm by electrical and pharmacological means. The former may use transthoracic or catheter-based energy delivery systems. The latter may use intravenous or oral drug approaches. Part 3, to be published in a subsequent edition of PACE will deal with the maintenance of sinus rhythm.

Rhythm management in atrial fibrillation--with a primary emphasis on pharmacological therapy: Part 1.

Atrial fibrillation (AF) is the most common, sustained, symptomatic tachyarrhythmia that clinicians are called upon to manage. Management strategies include ventricular rate control coupled with anticoagulation, versus restoration and maintenance of sinus rhythm. Rate control may be achieved pharmacologically, with agents that impair AV nodal conduction directly and/or by increasing parasympathetic/sympathetic balance, or by modifying or ablating the AV nodal region anatomically. Rhythm control may be achieved by electrical or pharmacological conversion followed by maintenance of sinus rhythm by pharmacological (or occasionally ablative) therapies. This article will present current approaches to rate and rhythm control issues in AF. Part 1, the current manuscript, details approaches to rate control and includes a drug selection algorithmic conclusion. It also introduces the subject of the pursuit of sinus rhythm. Parts 2 and 3, to be published in subsequent editions of PACE, will deal with therapeutic measures to restore and maintain sinus rhythm.

An inexpensive dual-excitation apparatus for fluorescence microscopy.

Ion sensitive indicator molecules can be employed in conjunction with fluorescence microscopy in single cells to measure rapid changes in the intracellular concentration of several ionic species. A number of these probes (e.g. fura-2) require the capability of measuring emission intensity at two excitation wavelengths to quantitate properly intracellular ion concentration. We have developed a simple dual-excitation apparatus for use in such applications. The apparatus switches the excitation filter within 150 ms. This economical apparatus is well suited in situations where the ionic concentration of interest is changing relatively slowly. Moreover, by synchronizing the device's action with an external stimulus, rapid and reproducible ionic changes in excitable tissue also can be measured.