Episodes Of Severe Bradycardia Research Articles

Abstract 15372: The Lewis Lead

The Lewis lead is a modified ECG configuration that can enhance the amplitude of the atrial electrical activity and is useful when the atrial activity cannot be discerned in the standard ECG. The configuration involves applying the right arm electrode on the manubrium, left arm electrode to the 5th intercostal space on the right sternal border, left leg electrode over the right lower costal margin and right leg electrode in the standard position. The ECG is then interpreted in lead I and II. Herein we present a case where the Lewis lead aided in the diagnosis of complete heart block with underlying atrial fibrillation. Case Presentation: A 75 year old female with severe tricuspid regurgitation was admitted for tricuspid valve replacement. She had previous paroxysmal atrial fibrillation status post pulmonary vein isolation. The preoperative ECG revealed normal sinus rhythm. Postoperatively, ECG demonstrated a narrow complex ventricular rhythm at 70 beats per minute. No atrial activity could be clearly discerned (Image 1). The epicardial atrial wire placed intraoperatively was not functioning, therefore atrial electrogram could not be obtained. It was unclear from repeat ECGs if there was sinus arrest or atrial fibrillation in the atria. The Lewis lead was then utilized and revealed underlying atrial fibrillation (Image 1); together, this was consistent with atrial fibrillation and complete heart block with a junctional escape rhythm. The rhythm did not recover and there was progressive conduction system disease with widening of the QRS and episodes of severe bradycardia. She underwent pacemaker implantation. Discussion: By utilizing the Lewis lead we were able to establish the atrial rhythm and differentiate between atrial fibrillation and sinus arrest. The Lewis lead can also help narrow the differential for wide complex tachycardia by magnifying the p wave, thus making it easier to detect ventriculoatrial dissociation, a hallmark feature of ventricular tachycardia.

Frequency of cardiac arrhythmias in older adults: Findings from the Subclinical Atrial Fibrillation and Risk of Ischemic Stroke (SAFARIS) study

BackgroundProlonged monitoring of cardiac rhythm has been used to screen for subclinical atrial fibrillation (AF); little is known about other arrhythmias in the general population, especially in the elderly, who are at higher risk of arrhythmias. MethodsWe evaluated the frequency of arrhythmias in the tri-ethnic (white, Black, Hispanic), community-based Subclinical Atrial Fibrillation and Risk of Ischemic Stroke (SAFARIS) study using a patch-based recorder for up to 14 days in 527 participants free of AF, congestive heart failure (CHF) or history of stroke. Differences according to gender, age, ethnicity and presence of hypertension, diabetes and pertinent ECG and echocardiographic variables were examined. ResultsMean age was 77.2 ± 6.8 years (37.2% men, 62.8% women). AF was present in 10 participants (1.9%), only 2 of them symptomatic. Supraventricular tachycardia (SVT) and ventricular tachycardia (VT) episodes were observed in 84.4% and 25.0% but only 13.5% and 10.6% of participants reported symptoms, respectively. Severe bradycardia (<40 bpm) was present in 12.5%. Sinus pauses and high-degree atrioventricular blocks were infrequent (2.1% and 1.5%, respectively). Most arrhythmias were more frequent in participants > 75 years; ventricular arrhythmias and severe bradycardia were more common in men. Whites had significantly more episodes of AF than Hispanics, SVT than Blacks and VT ≥ 10 beats than Hispanics and Blacks. Hypertensives had more episodes of severe bradycardia. LV hypertrophy or LVEF <55% were associated with more frequent ventricular and supraventricular arrhythmias. ConclusionsProlonged cardiac rhythm monitoring revealed moderate frequency of AF, but higher than expected frequencies of AF-predisposing arrhythmias. Ventricular arrhythmias were relatively frequent, whereas severe bradyarrhythmias were infrequent.

A Nearly Lethal Screw: An Unusual Cause of Recurrent Bradycardia and Asystole Episodes after Fixation of the Cervical Spine

We present a case of a 51-year-old man who was injured in a bicycle accident. His main injury was an unstable fracture of the cervical and thoracic vertebral column. Several hours after his arrival to the hospital the patient underwent open reduction and internal fixation (ORIF) of the cervical and thoracic spine. The patient was hospitalized in our critical care unit for 99 days. During this time patient had several episodes of severe bradycardia and asystole; some were short with spontaneous return to sinus and some required pharmacological treatment and even Cardiopulmonary Resuscitation (CPR). Initially, these episodes were attributed to the high cervical spine injury, but, later on, CT scan suggested that a fixation screw abutted on the esophagus and activated the vagus nerve by direct pressure. After repositioning of the cervical fixation, the bradycardia and asystole episodes were no longer observed and the patient was released to a rehabilitation ward. This case is presented in order to alert practitioners to the possibility that, after operative fixation of cervical spine injuries, recurrent episodes of bradyarrhythmia can be caused by incorrect placement of the fixation screws and might be confused with the natural history of the high cervical cord injury.

Effects of the dexmedetomidine, midazolam, butorphanol, and atropine combination on plasma oxidative status and cardiorespiratory parameters in raccoon dogs (Nyctereutes procyonoides)

Oxidative stress in the body occurs when the production of free radicals overwhelms the antioxidant defence systems. This study aimed to investigate the effects of a combination of dexmedetomidine, midazolam, butorphanol, and atropine (DMBA) as an anaesthetic on plasma oxidative status in twelve raccoon dogs. Baseline measures were recorded prior to anaesthesia, and then the animals were anaesthetised with the combination of dexmedetomidine (25 ug/kg), midazolam (0.45 mg/kg), butorphanol (0.25 mg/kg), and atropine (0.035 mg/kg). Temperature, respiratory rate, haemoglobin saturation by oxygen, pulse rate, systolic arterial pressure, diastolic arterial pressure, and mean arterial pressure were continually monitored. Blood pressure was significantly decreased at 30 to 60 min (P < 0.05). Pulse rate ranged from 96 to 123 bpm, without episodes of severe bradycardia or tachycardia. Blood samples were collected from saphenous venipuncture at 0, 0.5, 1, and 24 h before, during, and after anaesthesia. Plasma superoxide dismutase, glutathione peroxidase, and catalase activity, and malondialdehyde concentrations were measured by colorimetry, and plasma vitamin E level was determined by high-performance liquid chromatography. Superoxide dismutase and glutathione peroxidase activities increased significantly (P < 0.05) at 0.5 h, and then gradually decreased to baseline values after 1 h. Catalase activity increased significantly (P < 0.05) at 0.5 h, 1 h, and then gradually decreased to baseline values after 24 h. There was no significant change in vitamin E level (P < 0.05).The concentration of malondialdehyde decreased significantly at 0.5, 1, and 24 h after injection (P < 0.05). The results show that the administered dose of dexmedetomidine, midazolam, butorphanol, and atropine has antioxidant effects in raccoon dogs. Our study is the first to demonstrate that dexmedetomidine, midazolam, butorphanol, and atropine exert antioxidant effects, which may be exploited to alleviate the stress of examination and research at veterinary clinics.

Abstract 15839: Effect of Serotonin Neuron Depletion on Arterial Blood Pressure Regulation in Young Rats

Infants dying of Sudden Infant Death Syndrome (SIDS) have reduced brainstem serotonin (5-hydroxytryptamine, 5-HT) where some cases die following episodes of severe bradycardia and hypoxemia. The specific role of central 5-HT in resting arterial blood pressure (BP) and on baroreflex sensitivity during neonatal life has not been studied. In adult animals, systemic depletion of 5-HT increases BP with no effect on heart rate (HR) and reduces the sensitivity of the baroreflex. Other studies have also shown that a loss of central 5-HT beginning in embryogenesis reduces resting BP and HR in adulthood. Based on these reports, we hypothesized that loss of brainstem 5-HT neurons in the neonatal period would reduce baseline BP and HR as well as reduce baroreflex gain. To test this, we utilized 3-week old Sprague Dawley rats treated centrally with 5,7-dihydroxytryptamine (5,7-DHT, n=4; ~120 ug in saline, i.c.v.), a chemical that is toxic to serotonergic neurons. Littermate controls were injected with saline (CTRL, n=5, ~3ul, i.c.v.). We measured BP with a femoral artery catheter. HR was derived from BP. Following a recovery period, we measured resting variables for 15 minutes and then injected phenylephrine (PE; 3mg/kg s.c.) followed by sodium nitroprusside (SNP; 2.5mg/kg s.c.), separated by 15 minutes, to induce pressor or depressor responses, respectively. For both responses, baroreflex gain was calculated as the [[Unable to Display Character: &amp;#8710;]]HR at the maximum [[Unable to Display Character: &amp;#8710;]]BP following drug injection. We found that a loss of 5-HT neurons did not alter baseline BP (p&gt;0.05) but did reduce baseline HR when compared to control littermates (p&lt;0.02). 5-HT neuron deficiency tended to reduce baroreflex gain in response to PE (CTRL: -2.756 ± 0.483 beats/mmHg; 5,7-DHT: -1.499 ± 0.348 beats/mmHg; p=0.058), but not SNP (CTRL: -2.408 ± 0.351 beats/mmHg; 5,7-DHT: -3.316 ± 1.214 beats/mmHg; p&gt;0.05). Our data indicate that brainstem 5-HT maintains resting HR, and is involved in baroreflex control of HR in response to hypertensive stimuli. Reduced brainstem 5-HT may predispose an infant to SIDS via altered autonomic control of BP and HR. The role of 5-HT in BP regulation during hypoxic conditions remains to be elucidated.

Efficacy and safety of ivabradine in chronic heart failure across the age spectrum: insights from the SHIFT study

To test whether the efficacy and safety of the selective heart rate-reducing agent ivabradine changes according to age in chronic heart failure (HF) patients. The ivabradine and placebo arms of SHIFT, which enrolled 6505 chronic HF patients, were combined and age distribution was divided by quartiles to give four groups (<53 years, n = 1522; 53 to <60 years, n = 1521; 60 to <69 years, n = 1750; and ≥69 years, n = 1712). The effects of ivabradine on cardiovascular outcomes, changes in heart rate, and adverse events, particularly bradycardia, were evaluated according to age group. A subgroup (602 patients) underwent 24 h ambulatory ECG Holter monitoring. The relative risk of the primary endpoint (cardiovascular death or hospitalization for worsening HF) was reduced by ivabradine in all age groups, ranging from 38% [hazard ratio (HR) 0.62, 95% confidence interval (CI) 0.50-0.78, P < 0.001] in the youngest patients <53 years to 16% (HR 0.84, 95% CI 0.71-0.99, P = 0.035) in the oldest patients ≥69 years. Ivabradine up-titration reduced heart rate similarly in all age groups, by 11 b.p.m. As anticipated, bradycardia and phosphenes occurred more frequently with ivabradine, at a similar rate whatever the age. In the Holter substudy, there were no episodes of severe bradycardia and no clinically relevant pauses with ivabradine in any age group. Age does not limit the appropriate use of ivabradine in patients with chronic HF and systolic dysfunction. The safety and efficacy of ivabradine are comparable across all age groups.

Long‐Term Outcomes of Ivabradine in Inappropriate Sinus Tachycardia Patients: Appropriate Efficacy or Inappropriate Patients

Inappropriate sinus tachycardia (IST) is characterized by persistent and disproportional elevation of heart rate (HR). Ivabradine has been successfully used in some patients. Twenty-four patients (18 women, 41 ± 13 year olds) were diagnosed with IST according to current guidelines criteria. Patients were treated with 5-7.5 mg of ivabradine twice a day. Twenty-four-hour Holter recordings and the SF-36 Health Survey were performed at 6 months to evaluate both HR control and clinical status. Holter recordings before and after 6 months on treatment showed a significant reduction in the average maximal HR of 155 ± 18 beats/min versus 132 ± 16 beats/min, mean HR of 97 ± 6 beats/min versus 79 ± 8 beats/min (mean daytime HR of 103 ± 8 beats/min vs 84 ± 10 beats/min) and minimal HR of 58 ± 12 beats/min versus 48 ± 7 beats/min (Wilcoxon analysis, P < 0.05). The SF-36 mean score showed a significant improvement on ivabradine treatment (57 ± 23 vs 76 ± 20), with a better physical and mental status scores (56 ± 25 vs 74 ± 22 and 58 ± 24 vs 78 ± 18, respectively) (Wilcoxon analysis, P < 0.001). Mean dose of ivabradine was 5.8 ± 1.4 mg. No episodes of severe bradycardia or syncope were reported. After 1 year, patients were asked to stop treatment to reevaluate the situation. Twenty patients were on treatment and only 10 patients accepted to stop ivabradine. Only two patients (20%) remained on IST criteria. IST patients treated with ivabradine showed both HR normalization and quality-of-life improvement maintained in the long-term follow-up. Stopping ivabradine after 1 year unexpectedly showed that HR remained in the normal limits in 80% of the patients.

Anaesthesia and cardiopulmonary effects of tiletamine-zolazepam/xylazine/tramadol and its effects on nitric oxide, plasma endothelin, 6-keto-PGF1α and thromboxanes B2 in miniature pigs

This study focused on anaesthesia and cardiopulmonary effects of tiletamine-zolazepam/xylazine/tramadol in miniature pigs and its effects on endothelium-derived vasoactive factors. A total of 14 eight-month-old Chinese experimental miniature pigs were used in this study. Tiletamine-zolazepam (3.5 mg·kg-1), xylazine (1.32 mg·kg-1) and tramadol (1.8 mg·kg-1) were administered i.m.; blood pressure and heart rate were recorded. At the same time, blood was collected through precaval vein, and nitric oxide, endothelin, 6-keto-PGF1α and thromboxanes B2 were determined by colorimetry and radioimmunoassay. The mean times to dorsal recumbency, duration of immobilization, standing and walking were 2.26 ± 0.72, 87.57 ± 9.61, 25.63 ± 12.55 and 36.70 ± 14.53 min, respectively. Blood pressure was significantly changed at 10 and 80 min (P &lt; 0.01), and the heart rate ranged from 89 to 134 bpm without episodes of severe bradycardia or tachycardia. Significantly positive correlation was observed between endothelin, thromboxanes B2 and blood pressure as well as the heart rate (P &lt; 0.05). There was negative correlation between PGI2 and blood pressure as well as heart rate (P &lt; 0.05). The results showed that endothelin, 6-keto-PGF1α and thromboxanes B2 participated in the changing of cardiopulmonary parameters which were caused by tiletamine-zolazepam-xylazine-tramadol anaesthesia in miniature pigs, and the 6-keto-PGF1α, ET and TXB2 concentrations in plasma participated in the changing of blood pressures during anaesthesia. Therefore, we can recommend tiletamine-zolazepam/xylazine/tramadol for anaesthesia in pigs, and this study also contributes to the evaluation of the effect of endothelium-derived vasoactive factors during anaesthesia.

Dysautonomia From Bilateral Carotid Artery Dissection

The mechanisms of dysautonomia from carotid artery dissection were discussed recently in Circulation . A case was presented of a 49-year-old woman with a history of hypertension and vasovagal syncope who developed abrupt slurred speech and left hemiplegia.1 She had a right internal carotid artery dissection and right cerebral hemispheric infarction involving the insular cortex. During her hospitalization, the patient had episodes of severe bradycardia that Dulay et al1 attributed to “mechanical pressure to an already sensitive carotid sinus from thrombus secondary to a dissection of the internal carotid.” Sarikaya et al2 argued that disrupted descending autonomic pathways from the infarcted insular cortex were responsible. Right-sided insular lesions are known to cause bradyarrhythmias.3 We present a case of bilateral carotid artery dissection in which dysautonomia occurred in the absence of cortical damage. A 47-year-old right-handed woman with rheumatoid arthritis experienced symptoms of an apparent upper respiratory infection with a persistent cough after the syndrome resolved. After …

An uncommon case of right-sided throat pain and swallow syncope

A 63-year-old man presented with recurrent syncopal attacks associated with swallowing and right-sided throat pain. Immediately after admission, he presented a 16-s asystolia. The patient's clinical history was unremarkable except for previous postimplant periodontitis. Several episodes of severe bradycardia and sinus pauses, always associated with painful deglutition, were recorded subsequently. X-ray orthopanthomography and magnetic resonance imaging of the neck confirmed several areas of periodontitis around the previous dental implants and right mastoid inflammation. A barium swallow and fibre-optic endoscopy also revealed a small sliding hiatus hernia and distal chronic oesophageal inflammation. Despite complete dental curettage, antibiotics and antigastro-oesophageal reflux therapy, only partial relief of the pain and incomplete resolution of the arrhythmic disorder were obtained after 3 weeks, and the patient underwent pacemaker implantation. At 1-month follow-up, however, he reported the complete relief of the throat pain; subsequent Holter monitoring showed normal sinus rhythm, without pacemaker-induced electrical activity.

The haemodynamic effect of thoracoscopic cardiac sympathectomy

A patient with angina pectoris who had been successfully treated by thoracoscopic cardiac sympathectomy was scheduled to have scalp debridement under general anaesthesia for a scald burn. There were haemodynamic changes during and after the operation including anaesthetic induction, endotracheal intubation, maintenance, and early recovery period. The sympathetic denervated heart showed little chronotropic response to anaesthetic and surgical stimulation. On the contrary, the parasympathetic response was predominant. An episode of severe bradycardia occurred during endotracheal suctioning prior to extubation. The haemodynamic response to cardiac sympathetic denervation corresponded to the efferent effect of beta-receptor blockade

Vagal schwannoma of the cerebello-medullary cistern presenting with hoarseness and intractable tinnitus: a rare case of intra-operative bradycardia and cardiac asystole

Schwannomas arising from the lower cranial nerves (IX-XI) are rare, constituting only 3% of all intracranial schwannomas unassociated with neurofibromatosis. A great majority of these tumours present as jugular foramen lesions and less commonly they occur along the extracranial course of these nerves. An intracisternal location is extremely rare. We report a case of vagal schwannoma purely in the cerebello-medullary cistern causing distortion of the medulla oblongata. Total microsurgical excision of this tumor, arising from one of the rootlets of the vagus nerve, was achieved with preservation of the 9th, 10th and 11th cranial nerves.The intraoperative course was complicated by two episodes of complete cardiac asystole, each lasting for 4s, and six episodes of severe bradycardia. The patient was relieved of his intractable tinnitus but continued to have a hoarse voice due to an ipsilateral partial vocal cord palsy.

Heart rate response profiles during head upright tilt test in infants with apparent life threatening events

Sympatheticovagal imbalance causing episodes of severe bradycardia has been suggested as a cause of apparent life threatening events (ALTEs). The autonomic control of the heart rate in 18 infants with...

Severe Brady arrhythmia and Hypertension Following Dipyridamole Ingestion

We report an episode of severe bradycardia and hypotension following the administration of 400 mg oral dipyridamole in preparation for thallium-201 imaging in 2 patients. The severe effects in both were reversed with aminophylline infusion. Subsequent cardiac catheterization of 1 patient revealed occlusion of the right artery and 80% stenosis of the left main coronary artery. The response to dipyridamole by both patients suggests that careful monitoring should be performed when evaluating patients with a high pretest suspicion of multivessel coronary artery disease

Symptomatic disorders of cardiac conduction in childhood leukemia.

Two children suffering from leukemia developed cardiac arrhythmias severe enough to produce symptoms. Extensive leukemic infiltration led to heart block in one patient and palliative radiotherapy was beneficial. Episodes of severe bradycardia, due to increased vagal tone, occurred in the other child. Drug interaction was the likely cause.