Nonspecific Intraventricular Conduction Delay Research Articles

Cardiac Resynchronization Therapy in Non-Left Bundle Branch Block Morphologies

In select patients with systolic heart failure, cardiac resynchronization therapy (CRT) has been shown to improve quality of life, exercise capacity, ejection fraction (EF), and survival. Little is known about the response to CRT in patients with right bundle branch block (RBBB) or non-specific intraventricular conduction delay (IVCD) compared with traditionally studied patients with left bundle branch block (LBBB). We assessed 542 consecutive patients presenting for the new implantation of a CRT device. Patients were placed into one of three groups based on the preimplantation electrocardiogram morphology: LBBB, RBBB, or IVCD. Patients with a narrow QRS or paced ventricular rhythm were excluded. The primary endpoint was long-term survival. Secondary endpoints were changes in EF, left ventricular end-diastolic and systolic diameter, mitral regurgitation, and New York Heart Association (NYHA) functional class. Three hundred and thirty-five patients met inclusion criteria of which 204 had LBBB, 38 RBBB, and 93 IVCD. There were 32 deaths in the LBBB group, 10 in the RBBB, and 27 in the IVCD group over a mean follow up of 3.4 +/- 1.2 years. In multivariate analysis, no mortality difference amongst the three groups was noted. Patients with LBBB had greater improvements in most echocardiographic endpoints and NYHA functional class than those with IVCD and RBBB. There is no difference in 3-year survival in patients undergoing CRT based on baseline native QRS morphology. Patients with RBBB and IVCD derive less reverse cardiac remodeling and symptomatic benefit from CRT compared with those with a native LBBB.

Left-sided intraventricular conduction delay concealed by right bundle branch block

The electrocardiograms of a 69-year-old woman with severe heart failure showed a left-sided nonspecific intraventricular conduction delay (QRS duration, 0.13 seconds) characterized by notches and slurrings in the descending part of the R waves in the left precordial leads and in the ascending parts of the S waves in the right precordial leads. Subsequently, a complete right bundle branch block with wider QRS complexes (0.17 seconds) appeared. It is possible to consider that the left-sided nonspecific intraventricular conduction delay was concealed by the greater conduction delay occurring when the complete right bundle branch block was present. This would be in keeping with a previous study using Doppler tissue imaging in which this was postulated but where the corresponding electrocardiograms were not shown.

Evidence for Electrical Remodeling of the Native Conduction System with Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) improves hemodynamics and decreases heart failure symptoms. However, the potential of CRT to bring about electrical remodeling of the heart has not been investigated. We studied 25 patients, of whom 17 had a nonischemic cardiomyopathy, and 8 had an ischemic cardiomyopathy; 16 had left bundle branch block (LBBB), 1 right bundle branch block (RBBB), and 8 nonspecific intraventricular conduction delay. During routine device clinic visits, patients with chronic biventricular pacing (>6 months) were reprogrammed to VVI 40 to allow for native conduction to resume. After 5 minutes of native rhythm, a surface electrocardiogram (ECG) was recorded, and then the previous device settings were restored. This ECG was compared to the preimplant ECG. Preimplant mean ejection fraction was 19% (range, 10%-35%), and follow-up mean ejection fraction was 35% (12.5%-65%). Mean time from implant to follow-up ECG was 14 months (range, 6-31). The QRS interval prior to CRT was 155 +/- 29 ms, and shortened to 144 +/- 31 ms (P = 0.0006), and the QRS axis shifted from -1 +/- 59 to -26 +/- 53 (P = 0.03). There was no significant change in PR or QTc interval, or in heart rate. CRT leads to a decrease in the surface QRS duration, without affecting other surface ECG parameters. The reduced electrical activation time may reflect changes in the specialized conduction system or in intramyocardial impulse transmission.

Long-term survival with partial atrioventricular septal defect

Long-term survival of patients with partial atrioventricular (AV) septal defect without operative therapy is very rare. We report a 80-year-old female with partial AV septal defect who presented with progressive dyspnea, fatigue and palpitations. A 80-year-old female presented to our clinic complaining of palpitations, dyspnea and decline in general condition. Her history revealed that she had been suffering from paroxysmal palpitations and dyspnea for the last 20 years. The palpitations were usually of short-term duration lasting for a few minutes, though she described a few episodes that lasted longer and necessitated hospital admissions. Her dyspnea had became progressive for the last 2 years (NHYA functional class III). Hermedications were digoxin and amiadorone. The patient's blood pressure was 120/60 mm Hg and pulse rate was 52 beats/min. Auscultation of the heart revealed a 3/6 systolic murmur with maximum intensity at the apex. Lung fields were clear to auscultation. There was no sign of edema and jugular venous distension. Chest X-ray revealed a mild increase in heart size. The ECG showed normal sinus rhythm, first degree AV block, nonspecific intraventricular conduction delay and signs of left ventricular hypertrophy. Holter monitoring showed several bursts of atrial fibrillation. Transthoracic echocardiography (TTE) showed mildly enlarged left atrium, moderate septal hypertrophy, mild calcific aortic stenosis andmoderatemitral regurgitationwith eccentric jet directed toward the lateral and posterior atrium. TTE performed with an apical four-chamber view also disclosed a defect in the inferior part of the interatrial septum with left to

QRS Duration Does Not Predict Occurrence of Ventricular Tachyarrhythmias in Patients With Implanted Cardioverter-Defibrillators

The aim of this study was to determine whether QRS duration (QRSd) correlates with occurrence of ventricular arrhythmia in patients with coronary disease (CAD) receiving implantable cardioverter-defibrillators (ICDs). A QRSd measured on a standard electrocardiograph (ECG) correlates with total mortality risk in CAD patients at high risk for sudden death; however, the relationship between QRSd and risk of ventricular tachyarrhythmias (ventricular tachycardia/ventricular fibrillation [VT/VF]) is unclear. PainFREE Rx II was a randomized trial, comparing efficacy of antitachycardia pacing versus shock therapy for VT/VF in patients receiving ICDs. We retrospectively correlated the QRSd and specific ECG conduction abnormalities on the 12-lead ECG at study entry with occurrence of VT/VF in 431 patients with CAD enrolled in the trial. The QRSd was < or =120 ms in 291 of 431 (68%) patients. Left bundle branch block (LBBB) was present in 65 patients, right bundle branch block (RBBB) in 48 patients, and nonspecific intraventricular conduction delay (IVCD) was present in 124 patients. Over 12 months' follow-up, VT/VF occurred in 95 (22%) patients (22% of patients with QRSd < or =120 ms vs. 23% of patients with QRSd >120 ms, p = NS). Patients with LBBB were less likely to experience at least one VT/VF episode than patients with QRSd <120 ms. Patients with RBBB and nonspecific IVCD did not differ from patients with narrow QRS complexes with regard to occurrence of tachycardias. The QRSd and ECG conduction abnormalities are not useful to predict ICD benefit in patients having the characteristics of our study population. The utility of QRSd to predict VT/VF events in patients with CAD requires further prospective evaluation.

Development of atrio-ventricular block during adenosine infusion and incidence of subsequent pacemaker implantation: A retrospective study

Background Atrio-ventricular (AV) block during adenosine infusion complicates a small percentage of pharmacologic stress tests. The prognostic value of adenosine infusion-related AV block for predicting later conduction disturbances requiring permanent pacemaker (PPM) implantation is not known. Methods Retrospective analysis of the nuclear laboratory electronic data-base identified 125 patients, mean age 66.6 years (y) (SD 12.6), 65% females, who developed transient AV block during adenosine infusion. A control group of 337 consecutive patients mean age 64.4 y (SD 12.5), 63% females, without AV block on adenosine infusion was identified. Both sets of data were entered in the electrophysiology laboratory electronic data-base to identify those patients requiring permanent pacemakers (PPM). Results In the AV block group, 57 patients(46%) had baseline electrocardiogram (ECG) conduction disturbances (included sinus bradycardia, AV block, right or left bundle branch block and non-specific intraventricular conduction delay) versus 80 patients(24%) in the control group (p<0.001). A total of 8 patients received PPM, 50% due to sick sinus syndrome and 50% due to high-degree AV block. In the AV block group, the incidence of PPM implantation due to conduction disturbance was 2.4% (3 patients) by the end of 2.2 y (SD 1.44) after the adenosine infusion versus 1.5%(5 patients) by the end of 2.4 y (SD 0.26) in the control group (NS). The mean age for PPM implantation was 78.3 y (SD 6.3). Interestingly, ischemia localized to the right coronary artery territory was identified in 15 patients (12%) in the AV block group versus 10 patients (3%) in the control group (p<0.001). Conclusions The occurrence of AV block during adenosine infusion did not increase the incidence of conduction disturbances requiring PPM implantation during the time interval studied. Development of AV block during adenosine infusion occurred more frequently in patients with baseline ECG conduction abnormalities. Patients requiring PPM implantation were > 70 y regardless of the AV block status.

Isolated bundle branch block and left ventricular dysfunction

Background:Population studies have identified the presence of bundle branch block (BBB) as a risk factor for increased mortality in patients with known cardiac disease. It is unknown how chronic ventricular dyssynchrony resulting solely from conduction delay affects ventricular function. Methods and Results:Subjects were retrospectively identified from the University of California, San Francisco, electrocardiogram database with QRS prolongation. Subjects who had no evidence of heart disease and had baseline and serial studies evaluating ongoing risk of coronary artery disease status and left ventricular function were followed over time. Documentation of a minimum of 2 serial evaluations of cardiac status were present in a total of 51/176 (20%) subjects with isolated BBB who constitute the study population. After a mean follow-up of 52 ± 45 months—adjusting for differences due to age, sex, the presence of hypertension, hyperlipidemia, and diabetes mellitus—left ventricular ejection fraction diminished by −7.3 ± 12% per year in the isolated left BBB cohort versus −1.9 ± 4% in isolated right BBB cohort and −1.1 ± 3% reduction in the isolated nonspecific intraventricular conduction delay cohort (P =.019). Conclusions:Left bundle branch block itself may be a cause of ventricular dysfunction.

Continuous Spinal Anesthesia with Invasive Hemodynamic Monitoring for Surgical Repair of the Hip in Two Patients with Severe Aortic Stenosis

Continuous Spinal Anesthesia with Invasive Hemodynamic Monitoring for Surgical Repair of the Hip in Two Patients with Severe Aortic Stenosis

Continuous Spinal Anesthesia with Invasive Hemodynamic Monitoring for Surgical Repair of the Hip in Two Patients with Severe Aortic Stenosis

25%, severe global hypokinesis, and moderate mitral regurgitation. The patient also had a history of hypertension, atria1 fibrillation (AF), and noninsulin-dependent diabetes. His preoperative medications included digoxin, furosemide, enalapril, nitroglycerin patch, and glyburide. He had no known drug allergies. On physical examination, the patient was 180 cm in height and weighed 62 kg. Heart rate (HR) and blood pressure (BP) were 74 bpm and 120/70 mm Hg, respectively. Head and neck evaluation was significant for a Mallampati class II airway and decreased range of motion of the neck. The cardiac examination revealed an irregularly irregular heart beat with a grade 3/6 systolic murmur. The lungs were clear to auscultation. The electrocardiogram (ECG) revealed AF with a ventric

Clinical and electrophysiologic spectrum of fascicular tachycardias

The purpose of this report is to describe the clinical and electrophysiologic findings for patients with fascicular tachycardia (FT). Eight patients with FT, defined as tachycardia with HV interval during tachycardia less than that of HV of conducted impulses, were studied. ECG findings during FT included right bundle block and superior axis (four patients), right bundle branch block and inferior axis (one patient), and nonspecific intraventricular conduction delay (three patients). In three patients, entrainment as well as the ability to initiate and terminate the tachycardia favored a reentrant mechanism. In others, tachycardia initiation only over a critical range of paced cycle lengths and the incessant nature of the tachycardia or the presence of other atrial or ventricular foci favored a mechanism of either abnormal automaticity or triggered rhythms. Catheter ablation was successful in two of five patients in whom it was attempted. In conclusion, the ECG expression of FT is variable, depending on the site of origin of the arrhythmia in the ventricular specialized conduction system. Similarly, a variety of mechanisms and different foci may be associated with FT. Selected individuals may respond to catheter ablative therapy.

Bundle branch reentry: A mechanism of ventricular tachycardia in the absence of myocardial or valvular dysfunction

Objective, The aim of this study was to present bundle branch recentry as the mechanism of sustained ventricular tachycardia in the absence of myocardial or valvular dysfunction.Background. Previous reports have documented the relation between structural heart disease and bundle branch reentrant ventricular tachycardia. Myocardial or valvular dysfunction has thus far been recognised as the only anatomic substrate for the development of this tachycardia.Methods. Three patients with a wide QRS complex tachycardia underwent noninvasive and invasive cardiac evaluation and electrophysiologic studies to identify the substrate and mechanism of tachycardia. Catheter ablation of the right bundle branch using radiofrequency current was performed in each patient.Results. The patients were ail men (aged 54, 34 and 72 years) who presented with presyncope, palpitation and cardiac arrest, respectively. Electrocardiography during sinus rhythm revealed nonspecific intraventricular conduction delay in all three patients. Cardiac evaluation revealed no evidence of myocardial or valvular dysfunction in any patient. The baseline HV interval was prolonged in each patient (90, 100 and 75 ms, respectively). Programmed right ventricular stimulation initiated bundle branch reentrant tachycardia with typical left (three patients) and right (one patient) bundle branch block pattern. Catheter ablation of the right bundle branch using radiofrequency current abolished bundle branch reentry in all three patients. After 26-, 13- and 8-month follow-up periods, complete right bundle branch block persisted, and all three patients remained asymptomatic without antiarrhythmic drugs.Conclusions. Sustained bundle branch reentry can be a clinical arrhythmia in patients with no identifiable myocardial or valvular dysfunction except for isolated conduction abnormalities in the His-Purkinje system. This mechanism of tachycardia should be recognized during electrophysiologic evaluation, given the seriousness of this arrhythmia and the availability of effective treatment.

Cardiac arrhythmia following rapid imipramine withdrawal

Withdrawal symptoms following the discontinuation of tricyclic antidepressants (TCA) have been reported by several authors. Common withdrawal symptoms are gastrointestinal distress, insomnia, drowsiness or agitation, apathy, withdrawal, headaches, moodiness, and worsening recurrence of depressed mood (Anderson and Kristiansen 1959; Mann and MacPherson 1959; Kramer et al. 1961; Stein and Mendels 1980; Law et al. 1981). The incidence of reported withdrawal symptoms has varied considerably from 8 of 10 patients in one study to 2 of 20 in another (Mann and MacPherson 1959). Differences may depend on length of prior treatment and methodology (Shaten 1966). Boisvert and Chouinard (198 1) described a single case of a cardiac arrhythmia that was apparently related to imipramine (IMI) withdrawal, as it responded to restarting with IMI but not to benzodiazepines. Cardiac effects such as tachycardia, together with tachypnea and irritability, have also been observed in a few infants born to mothers on TCAs (Eggermont 1973; Webster 1973). We report the case of a woman with a preexisting nonspecific intraventricular conduction delay (IVCD) who developed multifocal premature ventricular contractions (PVCs), including pathological forms, after rapid withdrawal of IMI.

Transient atrioventricular block after open-heart surgery for congenital heart disease

The records of 22 patients with transient atrioventricular (AV) block after open-heart surgery for congenital heart disease from 1972 to 1978 were reviewed to determine the natural history of this entity. Preoperatively, no patient had AV block;3 had right bundle branch block (BBB), 1 had left BBB and 5 had nonspecific intraventricular conduction delay. Complete AV block developed in 20 patients and Mobitz II AV block in 2. Transient AV block occurred intraoperatively in 14 patients and within 48 hours postoperatively in 8;AV block persisted for ≥ 48 hours postoperatively in all patients, for a mean of 7.3 days (range 2 to 28). During a follow-up of 5.5 years (range 2.5 to 10), late AV block developed in 2 patients. None of the 18 patients whose escape QRS complex morphology during AV block was similar to the final QRS complex during normal sinus rhythm or atrial fibrillation with AV conduction had late AV block, whereas 2 of the 4 in whom it differed did (p < 0.01). There was no difference in the escape rate between the 2 groups. Thus, late development of high-grade AV block is infrequent among patients with transient postoperative AV block. An escape QRS complex during postoperative AV block that differs from the QRS complex seen on recovery of normal sinus rhythm or atrial fibrillation with anterograde conduction may identify those at high risk of late AV block.

Exercise-induced bundle branch block

Exercise-induced bundle branch block (BBB) is poorly understood. An investigation was made of its clinical, electrocardiographic, coronary angiographic, and myocardial scintigraphic characteristics, with follow-up data in 16 patients, aged 59 ±9 (mean ± standard deviation) years, 11 who had left BBB and 5 who had right BBB. Fourteen had a preexisting baseline electrocardiographic abnormality; 11 had either incomplete BBB or nonspecific intraventricular conduction delay. Heart rates at onset of exercise BBB varied from 70 to 166 beats/min and in 9 patients the rates at BBB onset and offset appeared to be related, occurring within 8 beats/min of each other. Coronary artery disease (CAD) was diagnosed in 10 patients, cardiomyopathy in 2, and probable coronary spasm in 2. One patient had ventricular arrhythmias of uncertain origin, and 1 appeared to have no cardiac disease. Three patients had reversible thallium perfusion defects consistent with ischemia concurrent with developing BBB. The 3 patients in whom exercise BBB persisted all had CAD. Over a mean of 28 months of follow-up, only 1 patient had a morbid cardiac event—nonfatal myocardial infarction—and 2 died from noncardiac causes. Thus, exercise BBB primarily occurs in the context of cardiac disease, most commonly CAD, and concurrent ischemia may be demonstrable; the presence of “rate relation” does not militate against CAD.