Prognosis and rehabilitation in bundle branch block and atrioventricular block in a hospital study.
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Adult↗
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Results for “Atrioventricular Block”
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[Congenital atrioventricular block].
Congenital atrioventricular block is defined (Yater) as a documented conduction defect in a young subject with unquestionable bradycardia in the absence of a history of infection which might have caused the condition after birth. It is a rare condition (1 out of 20,000 births) and may be isolated or associated with another congenital malformation. Four cardiac malformations are classically associated: endomyocardial fibrosis, morphological abnormalities close to the conduction system: corrected transposition, left isomerism; patent ductus arteriosus and atrial septal defect apparently unrelated but the most common; the association of mitral regurgitation in adults, although the significance is not very clear. Isolated block is often observed in patients with mothers suffering from autoimmune disease, often clinically latent. Anti Ro/SS-A and La/SS-B antibodies cross into the foetal circulation and cause inflammation of the conduction tissues but the causal mechanism is not known. The diagnosis of the conduction defect is sometimes made during foetal life by echocardiography. After birth, the diagnosis is made by electrocardiography but the block is not always complete or permanent, its degree often increasing with time. In addition, in advanced degrees of block, the escape rhythm tends to slow down. Long-term follow-up studies have revised the previously considered good prognosis of isolated congenital atrioventricular block but advances in cardiac pacing provide satisfactory treatment. In the foetus, isolated atrioventricular block is usually associated with an escape rhythm > 60/min and enables normal vaginal delivery; a low heart rate < 55/min and anasarca carry a poor prognosis. In the neonate, pacing is indicated in babies with cardiac failure and a heart rate < 55/min. Follow-up by Holter monitoring, exercise testing and echocardiography is justified in children and adolescents; the patients may become symptomatic at any age. Pacing is essential in symptomatic cases (malaise, ventricular dysfunction) and useful in cases with long QT intervals, frequent ventricular extrasystoles and wide ventriculogrammes. Pacing is not always easy in children. Epicardial pacing by thoracotomy or an epigastric approach is possible but endocavitary pacing is to be preferred using thin pacing catheters introduced via the subclavian vein and small pacemakers implanted in a sub or prepectoral site. A pacing mode which restores the normal atrioventricular sequence is theoretically superior to single ventricular pacing even if rate responsive frequency.
Adult↗
[Complete congenital atrioventricular block].
Congenital atrioventricular block is defined (Yater) as a documented conduction defect in a young subject with unquestionable bradycardia in the absence of a history of infection which might have caused the condition. This condition may be isolated or associated with structural cardiac disease. Isolated block is often observed in patients with mothers suffering from autoimmune disease, often clinically latent. Anti-Ro/SS-A and La/SS-B antibodies cross into the fetal circulation and cause inflammation of the fetal conduction system. The diagnosis of the conduction defect is sometimes made during fetal life by echocardiography. Echocardiography assesses fetal hemodynamic status and may detect signs of fetal deterioration. Long-term follow-up studies have revised the previously considered good prognosis of isolated congenital atrioventricular block but advances in cardiac pacing provide satisfactory treatment. Follow-up by Holter monitoring, exercise testing and echocardiography is justified in children and adolescents; the patients may become symptomatic at any age. Indications for permanent pacing in pediatric patients have been difficult to determine due to the lack of data from controlled studies and multicenter trials. Pacing is not always easy in children. Epicardial pacing is advocated in small patients (< 5 years of age or 30 kg in weight). A pacing mode which restores the normal atrioventricular sequence is theoretically superior to single ventricular pacing even with rate responsive frequency.
Adolescent↗
Alpha 2-adrenergic receptor agonist effects on supraventricular and ventricular automaticity in dogs with complete atrioventricular block.
Complete atrioventricular block was induced in 26 pentobarbital-anesthetized dogs to determine the effects of the alpha 2-adrenergic receptor agonists, xylazine and medetomidine, on supraventricular and ventricular automaticity. Prazosin and atipamezole, alpha-adrenoceptor antagonists, were administered to isolate alpha 1- or alpha 2-adrenoceptor effects. Six dogs served as controls and were given glycopyrrolate (0.1 mg/kg of body weight, IV) and esmolol (50 to 75 micrograms/kg/min, IV) to induce parasympathetic and beta 1-adrenergic blockade, respectively. Eight dogs were given sequentially increasing doses of xylazine (n = 5), 0.000257 mg (10(-9)M) to 25.7 mg (10(-4)M) and medetomidine (n = 3), 0.000237 mg (10(-9)M) to 2.37 mg (10(-5)M) after parasympathetic and beta 1-adrenergic blockade. Twelve dogs were given xylazine (n = 6, 1.1 mg/kg, IV) or medetomidine (n = 6, 0.05 mg/kg, IV) after parasympathetic and beta 1-adrenergic blockade. Three dogs given xylazine and 3 dogs given medetomidine were administered prazosin (0.1 mg/kg, IV) followed by atipamezole (0.3 mg/kg, IV). The order of prazosin and atipamezole was reversed in the remaining 3 dogs given either xylazine or medetomidine. Complete atrioventricular block and administration of glycopyrrolate and esmolol resulted in stable supraventricular and ventricular rates over a 4-hour period. Increasing concentration of xylazine or medetomidine did not cause significant changes in supraventricular or ventricular rate. Xylazine and medetomidine, in the presence of the alpha-adrenoceptor antagonists, prazosin (alpha 1) and atipamezole (alpha 2), did not cause significant changes in supraventricular or ventricular rate.(ABSTRACT TRUNCATED AT 250 WORDS)
Adrenergic alpha-Agonists↗
The safety of adenosine pharmacologic stress testing in patients with first-degree atrioventricular block in the presence and absence of atrioventricular blocking medications.
BACKGROUND: Pharmacologic stress testing in conjunction with radionuclide myocardial perfusion imaging may be used in the diagnosis of coronary artery disease and risk assessment. Adenosine can cause atrioventricular nodal (AV) block during infusion. In this study, we evaluated whether patients with baseline first-degree AV block could safely undergo adenosine stress testing. METHODS AND RESULTS: We evaluated the frequency of second- and third-degree AV block in patients with baseline first-degree AV block during adenosine stress testing, in the presence and absence of AV blocking medications (digitalis, beta-blockers, diltiazem, verapamil). Six hundred consecutive patients underwent pharmacologic stress myocardial perfusion imaging with adenosine infusion at 140 microg/kg/min for 6 minutes. A total of 43 patients (7.16%) had baseline first-degree AV block (PR interval > 200 msec), and 557 patients had a baseline PR interval < 200 msec. Twenty-one of the 43 patients (48.8 %) had further prolongation of PR interval > 240 msec, compared with 58 of 557 patients (10.4%) in the control group (P < .0001). In 16 of the 43 patients (37.3 %), second-degree AV block developed, compared with 45 of 557 patients (8.0 %) in the control group (P < .0001). In 6 of the 43 patients (13.9%), third-degree AV block developed, compared with 6 of 557 patients (1.0%) in the control group (P < .0001). All types of AV block were short duration and were not associated with any specific symptoms. None of these episodes required specific treatment. The presence of AV blocking medications (digitalis, beta-blockers, diltiazem, verapamil) did not increase the incidence of AV block during adenosine infusion. CONCLUSION: In patients with baseline PR interval of more than 200 msec, the frequency of second- and third-degree AV block during adenosine stress testing was significantly higher than in patients with a normal baseline PR interval. AV blocking medications did not increase the incidence of second- and third-degree AV block during adenosine stress testing. We conclude that it is safe to perform adenosine pharmacologic stress testing in patients with baseline PR prolongation.
Adenosine↗
Optimized biventricular pacing in atrioventricular block after cardiac surgery.
BACKGROUND: Temporary pacing is required after open-heart surgery for treatment of heart block. Atrioventricular delay and ventricular pacing site might be manipulated to increase cardiac output. We hypothesized that by optimizing both atrioventricular delay and ventricular pacing site a 10% improvement in cardiac output would be observed compared with a standard pacing protocol. METHODS: Seven patients in first or third degree heart block after valve replacement surgery had temporary wires sewn to the right atrium, right ventricle, and left ventricle. Cardiac output was measured by integrating flow velocity from an ultrasonic aortic flow probe. After optimization of atrioventricular delays during atrial synchronous right ventricular pacing, the effects of ventricular pacing site were tested at the optimum atrioventricular delay for 10-second intervals. RESULTS: Biventricular pacing was beneficial in all patients with a mean increase of 22% in cardiac index over right ventricular pacing (1.95 L/min/m2 +/- 0.27 standard error of the mean (SEM) to 2.38 L/min/m2 +/- 0.27 SEM, p = 0.0012) and 14% over left ventricular pacing (2.08 L/min/m2 +/- 0.22 SEM to 2.38 L/min/m2 +/- 0.27 SEM, p = 0.0133). Comparing optimized with standard pacing for 30-second intervals yielded a mean increase of 10% in cardiac index over three respiratory cycles (2.87 L/min/m2 +/- 0.33 SEM to 2.60 L/min/m2 +/- 0.37 SEM, p = 0.009) and 17% at the corresponding end-expiratory beats (2.76 L/min/m2 +/- 0.33 SEM to 2.36 L/min/m2 +/- 0.36 SEM, p = 0.011). CONCLUSIONS: Biventricular pacing at optimum atrioventricular delay improves cardiac output in patients with postoperative heart block by at least 10% compared with standard pacing.
Blood Pressure↗
Trifascicular block with intermittent complete atrioventricular block in a child.
Trifascicular block, which consists of impaired conduction in the three main fascicles of the ventricular conduction system, may progress to high-grade or complete atrioventricular block. It rarely occurs in children with a structurally normal heart. We report a case of trifascicular block in a previously healthy 9-year-old girl. The patient presented with repetitive seizures. The electrocardiogram showed a complete right bundle branch block, left axis deviation, PR interval prolongation, and intermittent high-degree and complete atrioventricular block. She was successfully treated with a temporary pacemaker and her electrocardiogram returned to a normal sinus rhythm in 3 days. She has remained well over a 4-year follow-up. Although her cardiac enzyme levels were normal, the clinical course and electrocardiography findings suggested myocarditis. We emphasize the diagnosis of trifascicular block using electrocardiography; clinical outcome is good, if the patient is managed properly.
Child↗
Concealed paroxysmal atrioventricular block: diffuse congenital atrioventricular conduction system disorder with nonpropagated His bundle depolarizations.
A 2 1/2-year-old girl with bradycardia and left bundle branch block at birth began to experience "night cries" when deeply asleep. Electrophysiological study demonstrated congenital diffuse atrioventricular conduction disease with concealed paroxysmal atrioventricular block, nonpropagated His bundle depolarizations, severe sinus node abnormality, and a low atrioventricular junctional escape rhythm with probable reciprocation. After pacemaker implant, the "night cries" ceased.
Bradycardia↗
Management of fetal complete atrioventricular block.
Congenital atrioventricular block was diagnosed with B-mode and M-mode ultrasonography at the 30th week of gestation in a bradycardic fetus. Major anomalies were excluded and prenatal fetal well-being was monitored with daily B-mode and maternal perception of fetal movement to detect circulatory derangement at an early stage. Because of the sudden onset of circulatory failure, emergency Caesarean section was performed to save the otherwise normal fetus. Two days later, the infant developed ventricular fibrillation, for which surgical intervention was indicated. Pacemaking was effective in reestablishing the neonatal circulation.
Female↗
Atrioventricular block after reciprocating atrioventricular junctional tachycardia.
Short runs of symptomatic atrioventricular (A-V) block occurred after spontaneous cessation of reciprocating A-V junctional tachycardia in a patient with right bundle branch block, normal H-V interval and sinus nodal dysfunction. These episodes were characterized by long (more than 1 sec) P-P intervals during which the A deflections were not followed by His bundle electrograms. Three possible explanations are: (1) a posttachycardia-induced period of abnormally prolonged A-V nodal refractoriness; (2) pseudo-A-V block produced by concealed A-V junctional tachycardia, or (3) bradycardia-dependent (phase 4) A-V block at the "upper" His bundle, above the site from which the H deflection was recorded.
Atrioventricular Node↗
Risk of development of delayed atrioventricular block after slow pathway modification in patients with atrioventricular nodal reentrant tachycardia and a pre-existing prolonged PR interval.
AIMS: The objective of this prospective study was to assess risk factors for the development of atrioventricular block following slow pathway modification in patients with atrioventricular nodal reentrant tachycardia and a pre-existing prolonged PR interval. METHODS AND RESULTS: Of 346 consecutive patients with atrioventricular nodal reentrant tachycardia undergoing slow pathway modification, 18 patients (62 +/- 7 years; five females) were found to have a prolonged PR interval prior to ablation. Total elimination of the functional slow pathway was assumed if the antegrade effective refractory period following slow pathway modification was longer than the cycle length of atrioventricular nodal reentrant tachycardia. To detect atrioventricular node conduction disturbances, 24-h Holter recordings were performed 1 day prior to slow pathway modification, and 1 day, 1 week, 1, 3 and 6 months after the procedure. Six patients developed late atrioventricular block. The incidence of delayed atrioventricular block following successful slow pathway modification was higher in patients with, compared to patients without, prolonged PR interval at baseline (6/18 vs 0/328, P < .001). In the former group, the antegrade effective refractory period was longer in patients with, compared to those without, a delayed atrioventricular block (492 +/- 150 ms vs 332 +/- 101 ms, P < 0.05). The incidence of delayed atrioventricular block was higher in patients with total elimination of the slow pathway compared to patients without (5/7 vs 1/11, P < 0.01). CONCLUSIONS: Slow pathway modification in patients with atrioventricular nodal reentrant tachycardia and a prolonged PR interval is highly effective. However, there is a significant risk of development of delayed atrioventricular block, particularly when the procedure results in total elimination of the slow pathway.
Case-Control Studies↗
Incidence of complete atrioventricular block following attempted radiofrequency catheter modification of the atrioventricular node in 880 patients. Results of the Multicenter European Radiofrequency Survey (MERFS) The Working Group on Arrhythmias of the European Society of Cardiology.
UNLABELLED: The Multicenter European Radiofrequency Survey (MERFS) retrospectively analysed the incidence of procedure-related complications in 4463 patients who had undergone radiofrequency catheter ablation in 69 European institutions between 1987 and 1992. Of these 4463 patients, 880 underwent modification of the atrioventricular node to cure atrioventricular nodal reentrant tachycardia. This report presents a detailed analysis of the incidence of complete atrioventricular block with respect to the target site and the number of patients reported per institution. The most common complication of modification of the atrioventricular node was the unintended induction of complete atrioventricular block (41 of 880 patients, 4.7%). In 684 of 880 patients (78%), detailed information about the approached target site for modification of the atrioventricular node was available. Complete atrioventricular block occurred significantly more often in patients who underwent ablation of the fast pathway (19/361, 5.3%) or in whom ablation of the slow and fast pathway was attempted after failure at the initial site (4/25, 16%) than in patients who underwent slow pathway ablation (6/298, 2.0%, P < 0.05). The overall incidence of complete atrioventricular block was significantly higher (6.3%) in centres with limited experience in radiofrequency modification of the atrioventricular node ( < or = 30 patients treated; group I: n = 526) compared to centres that had treated > 30 patients (group II: n = 354; 2.3%; P < 0.05). In addition, in those patients in whom the target site was available, the incidence of complete atrioventricular block after fast pathway ablation was significantly higher in group I (n = 168 patients) when compared to group II (n = 193 patients) (7.7% vs 3.1%, P < 0.05) and also tended to be higher after slow pathway ablation in group I (2.4% in group I vs 1.5% in group II; P = ns). CONCLUSIONS: In this analysis of collaborative data, radiofrequency catheter modification of the atrioventricular node carried a risk of approximately 5% of complete atrioventricular block. The incidence of complete atrioventricular block was significantly higher in patients who underwent fast pathway ablation or fast and slow pathway ablation after failure at the initial site compared with slow pathway ablation. In addition, the results indicate that there is a learning curve, regarding the incidence of complete atrioventricular block, which is a significant complication of the procedure, when modifying the atrioventricular node. Thus, caution is recommended when performing radiofrequency modification of the atrioventricular node using the so-called anterior approach to abolish fast pathway conduction, especially when the experience of the institution or investigator/s is limited.
Atrioventricular Node↗
[Intermittent left bundle-branch block: normalization by atrioventricular block].
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Aged↗
[Atrioventricular block--electrocardiography of the bundle of His and classification of atrioventricular block].
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Adult↗
Hemodynamic effect of the ventricular pacing site in fetal lambs with complete atrioventricular block.
Complete atrioventricular (AV) block in hydrops fetalis is associated with high mortality. Fetal ventricular pacing to restore ventricular rate can be an effective procedure, however, no fetal data has shown an appropriate epicardial ventricular pacing site. To evaluate the hemodynamic effect of right and left ventricular pacing in fetal lambs with complete AV block, a fetal complete AV block model was created. Aortic pressure, central venous pressure, and QRS duration were measured, and right and left ventricular output was estimated in seven fetal lambs. The uterus was opened under maternal anesthesia, and under local anesthesia, catheters were inserted into the fetal superior vena cava and ascending aorta through a neck incision. Pacing leads were then sutured onto the fetal right and left ventricular epicardium via a midline thoracotomy. Complete AV block was created by cryoablation of the AV node. Ventricular output was estimated using echocardiography by a transuterine approach. Fetal hemodynamics were observed before AV block creation (control), and after complete AV block creation with the right and left ventricular pacing set at 150/min. The right ventricular output was 320 +/- 66 mL/kg per minute at control, decreased to 243 +/- 65 mL/kg per minute during right ventricular pacing (P < 0.05), and was 254 +/- 61 mL/kg per minute during left ventricular pacing. The left ventricular output was 224 +/- 98 mL/kg per minute at control, 176 +/- 77 mL/kg minute during right ventricular pacing, and 178 +/- 67 mL/kg per minute during left ventricular pacing. Biventricular (combined ventricular) output was 544 +/- 134 mL/kg per minute at control, 419 +/- 114 mL/kg per minute during right ventricular pacing, and 432 +/- 100 mL/kg minute during left ventricular pacing. Systolic aortic pressure was 62.2 +/- 8.7 mmHg at control, 55.2 +/- 9.5 mmHg during right ventricular pacing, and 53.4 +/- 9.1 mmHg during left ventricular pacing. Central venous pressure (CVP) was 2.6 +/- 0.5 mmHg at control, 4.0 +/- 2.7 mmHg during right ventricular pacing, and 4.4 +/- 2.5 mmHg during left ventricular pacing. The QRS duration was 51 +/- 54 ms at control, but lengthened to 87 +/- 19 ms during right ventricular pacing and to 78 +/- 21 ms during left ventricular pacing (P < 0.05). In conclusion, the right ventricular output decreased during right ventricular pacing in fetal lambs with complete AV block, while it was preserved during the left ventricular pacing. Left ventricular pacing might be superior for treating hydropic fetuses with complete AV block.
Analysis of Variance↗
Congenital complete atrioventricular block.
Congenital complete atrioventricular block is found in 1 of 22,000 live births. Over time, it has become apparent that these patients represent not a single distinct disease process, but several processes with the common manifestation of atrioventricular block. The evaluation of these patients to determine their risk of sudden death and need for pacing is not well defined.
Child↗
Myocardial bridging as a cause of paroxysmal atrioventricular block.
Paroxysmal atrioventricular (AV) block was induced by exercise in an otherwise healthy young man. The only abnormalities demonstrated at comprehensive cardiac evaluation were: 1) angiographic systolic narrowing of the left anterior descending coronary artery, and 2) reversible radionuclide hypoperfusion of the septum during exercise. It is postulated that ischemia of the conduction system due to systolic milking of the left anterior descending coronary artery was responsible for the paroxysmal AV block in this patient.
Adult↗
Effects of halothane, enflurane, and isoflurane on supraventricular and ventricular rate in dogs with complete atrioventricular block.
Complete atrioventricular (AV) block was produced in 32 chloralose-anesthetized autonomically intact dogs to determine the effects of halothane, enflurane, and isoflurane on supraventricular and ventricular rate. Halothane (n = 17), enflurane (n = 6), and isoflurane (n = 9) were administered in three separate experiments in sequential minimum alveolar concentration (MAC) multiples of 0.5, 1.0, 1.5, 2.0, 1.5, and 1.0. Supraventricular rate, ventricular rate, and mean arterial blood pressure (MAP) were measured and recorded at baseline and after a 20-minute equilibration period of each inhalation anesthetic at each MAC multiple. Increasing concentrations of enflurane and isoflurane significantly decreased supraventricular rate (P < .05). Ventricular rate was not significantly changed by sequential MAC multiples of halothane, enflurane, and isoflurane. Increasing concentrations of halothane, enflurane, and isoflurane significantly decreased MAP with enflurane producing the most significant decrease (P < .05). Ventricular arrhythmias occurred in 5 of 17 dogs anesthetized with halothane and 1 of 9 dogs anesthetized with isoflurane. Inhalation anesthesia can significantly decrease supraventricular rate and MAP, does not alter ventricular rate, and can produce ventricular arrhythmias in dogs with complete AV block.
Anesthesia, Inhalation↗