Rapid Ventricular Response Rates Research Articles

Cardiovascular changes in horses with atrial fibrillation and high thyroid hormone concentration: a case–control study

IntroductionHyperthyroidism is a predisposing factor for atrial fibrillation (AF) in humans. The relationship between high thyroid hormone (TH) and AF in horses has not been evaluated. ObjectivesThe aim of this study is to identify whether (1) high TH concentrations were present in horses with AF, (2) other cardiovascular effects were observed in horses with high TH and AF, and (3) TH status affected recurrence rate. AnimalsTwenty-three horses presented with naturally occurring AF. MethodsProspective case–control clinical study. Thyroid hormone concentration was measured in horses presenting with AF. Heart rate, electrocardiogram, blood pressure, and an echocardiogram were recorded as part of their clinical workup. Recurrence rate was determined by owner/veterinarian follow-up. ResultsHigh TH concentration was found in 60% of horses with AF. Horses in the high TH group had a higher heart rate (P=0.001), systolic blood pressure (P=0.019), left ventricular free wall thickness (P=0.026), relative wall thickness (P=0.041) and were more likely to have periods of AF with a rapid ventricular response rate (P=0.022). All horses were successfully converted to normal sinus rhythm. The likelihood of recurrence was not different between groups. ConclusionElevated TH concentration can be found in horses with AF. Other cardiovascular effects of high TH concentrations in other species were also present in horses with AF and elevated TH concentrations. This study recommends measuring TH concentrations in horses presenting for AF with a history of thyroid or iodine supplementation. This study also cautions against TH or iodine supplementation in healthy performance horses.

Impact of Physiologic Pacing Versus Right Ventricular Pacing Among Patients With Left Ventricular Ejection Fraction Greater Than 35%: A Systematic Review for the 2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society.

It is unclear whether physiologic pacing by either cardiac biventricular pacing (BiVP) or His bundle pacing (HisBP) may prevent adverse structural and functional consequences known to occur among some patients who receive right ventricular pacing (RVP). Our analysis sought to review existing literature to determine if BiVP and/or HisBP might prevent adverse remodeling and be associated with structural, functional, and clinical advantages compared with RVP among patients without severe left ventricular dysfunction (>35%) who required permanent pacing because of heart block. A literature search was conducted using MEDLINE (through PubMed) and Embase to identify randomized trials and observational studies comparing the effects of BiVP or HisBP versus RVP on measurements of left ventricular dimensions, left ventricular ejection fraction (LVEF), heart failure functional classification, quality of life, 6-minute walk, hospitalizations, and mortality. Data from studies that met the appropriate population, intervention, comparator, and outcomes of interest were abstracted for meta-analysis. Studies that reported pooled outcomes among patients with LVEF both above and below 35% could not be included in the meta-analysis because of strict relationships with industry procedures that preclude retrieval of industry-retained unpublished data on the subset of patients with preserved left ventricular function. Evidence from 8 studies, including a total of 679 patients meeting the prespecified criteria for inclusion, was identified. Results were compared for BiVP versus RVP, HisBP versus RVP, and BiVP+HisBP versus RVP. Among patients who received physiologic pacing with either BiVP or HisBP, the LV end-diastolic and end-systolic volumes were significantly lower (mean duration of follow-up: 1.64 years; -2.77 mL [95% CI -4.37 to -1.1 mL]; P=0.001; and -7.09 mL [95% CI -11.27 to -2.91; P=0.0009) and LVEF remained preserved or increased (mean duration of follow-up: 1.57 years; 5.328% [95% CI: 2.86%-7.8%; P<0.0001). Data on clinical impact such as functional status and quality of life were not definitive. Data on hospitalizations were unavailable. There was no effect on mortality. Several studies stratified results by LVEF and found that patients with LVEF >35% but ≤52% were more likely to receive benefit from physiologic pacing. Patients with chronic atrial fibrillation who underwent atrioventricular node ablation and pacemaker implant demonstrated clear improvement in LVEF with BiVP or HisBP versus RVP. Among patients with LVEF >35%, the LVEF remained preserved or increased with either BiVP or HisBP compared with RVP. However, patient-centered clinical outcome improvement appears to be limited primarily to patients who have chronic atrial fibrillation with rapid ventricular response rates and have undergone atrioventricular node ablation.

Atrial Fibrillation Pathophysiology and Prognosis

Atrial fibrillation (AF) is the most common sustained arrhythmia and is characterized by ineffective atrial contractions and often rapid ventricular response rates. It has been recognized that the risk of AF increases with age and the rise in AF incidence in recent decades is at least partly accounted for by the aging population in addition to the increase in other risk factors, including obesity.1,2 The global estimated prevalence of AF was >33 million in 2010,3 and projections indicate that its incidence and prevalence could potentially increase >2.5-fold by 2030.4 Although aging, hypertension, body mass index, structural heart disease, heart failure, and pulmonary disease are recognized clinical risk factors for the development of AF,5,6 advances in cardiovascular imaging, including novel echocardiographic techniques, cardiac MRI (CMR), computed tomography (CT), and positron emission tomography, have provided novel insights into AF pathogenesis, prediction, and natural history. Despite the use of novel imaging technologies and the use of sophisticated invasive ablative techniques and newer anticoagulation strategies, AF still comprises a considerable public health burden and results in major morbidity and expenditures.7,8 Thromboembolism and its sequelae account for much of this burden. Ineffective atrial contraction results in decreased flow and stagnation of blood in atrial structures, primarily the left atrial (LA) appendage (LAA), and AF itself may represent an inflammatory and procoagulable state, further contributing to thromboembolism pathogenesis.9,10 In addition, one has to take into account the company it keeps in that AF is associated with a significant number of comorbidities, which may independently contribute to thromboembolism and other adverse outcomes. Given this expanding burden and the challenges in developing effective management strategies for AF and its complications, workshops of the American Heart Association and the National Heart, Lung, and Blood Institute …

ST-elevation myocardial infarction caused by thromboembolism from the left atrial appendage

A 64-year-old gentleman was admitted for primary percutaneous coronary intervention (PCI) after he experienced chest pain while drinking alcohol in a pub. The electrocardiograms demonstrated atrial fibrillation (AF) with a rapid ventricular response rate and transient ST-segment elevation with loss of R waves in the anterior leads (Figure 1). Coronary angiography revealed a thrombotic occlusion of the distal segment of the left anterior descending artery (Figure 2). The proximal left anterior descending, circumflex and right coronary arteries were angiographically free from significant atherosclerotic changes. …

A Randomized Controlled Trial of Magnesium Sulfate, in Addition to Usual Care, for Rate Control in Atrial Fibrillation

We examine the safety and efficacy of magnesium sulfate infusion, in addition to usual care, for acute rate reduction in patients with atrial fibrillation and a rapid ventricular response rate. This was a prospective, randomized, double-blind, placebo-controlled trial of intravenous magnesium sulfate in adult emergency department patients with rapid atrial fibrillation. Study solutions were given in addition to any therapy the treating physician would normally consider appropriate, including the use of standard rate-reduction agents. Patients received either 20 mEq (2.5 g, 10 mmol) magnesium sulfate over a 20-minute period, followed by 20 mEq (2.5 g, 10 mmol) over a 2-hour period intravenously, or placebo. One hundred ninety-nine patients were randomized, 102 to receive magnesium sulfate and 97 to receive placebo. The antiarrhythmic drug most commonly used by treating physicians was digoxin. Magnesium sulfate was more likely than placebo to achieve a pulse rate of less than 100 beats/min (63 [65%] of 97 versus 32 [34%] of 93, relative risk [RR] 1.89; 95% confidence interval [CI] 1.38 to 2.59; P <.0001) and more likely to convert to sinus rhythm (25 [27%] of 94 patients versus 11 [12%] of 91 patients; RR 2.20; 95% CI 1.15 to 4.21; P =.01). Comparative mean pulse rate reductions in the magnesium sulfate group did not reach predetermined clinical significance levels (> or =15 beats/min reduction) at any of the measured time points. Magnesium sulfate was more likely to be associated with an adverse event (14 [15%] of 95 patients versus 5 [5%] of 92 patients; RR 2.71; 95% CI 1.02 to 7.23; P =.04). Magnesium sulfate, when used to supplement other standard rate-reduction therapies, enhances rate reduction and conversion to sinus rhythm in patients with rapid atrial fibrillation.

Overfeeding in a patient with kwashiorkor syndrome

The patient was a 56-y-old white female admitted on October 21, 1995, for acute abdominal pain with an ultimate diagnosis of mesenteric ischemia and gangrenous cholecystitis. She subsequently underwent a cholecystectomy and small and large bowel resection with a jejunocolostomy. On admission she was 5 ‘5” ( 165 cm), 102 pounds (46.3 kg), with an ideal body weight of 125 pounds. An albumin level done postoperatively was 2.6 g/dL. Postoperatively she was ventilator-dependent and had an ileus. She was started on 1000 kcaYd of total parenteral nutrition (TPN) which included 19% of calories as protein (47.5 g/d). On October 24 and 25, she became febrile and was re-explored to rule out ischemic small bowel. Upon re-exploration, no necrotic small bowel was found. On October 26, she extubated herself and was ultimately transferred to the ward. Her TPN was increased to 1600 kcal/d, 19% of calories as protein (76 g/d). She did well until October 31, when she developed two fistulas through her abdominal wound. She was kept NPO, the TPN was continued, and somatostatin was begun. Because she was felt to be hypermetabolic, her TPN was increased to 1800 kcaYd with 24% of calories as protein (108 g/d). Laboratory values revealed a total protein level of 5.3 g/dL and a serum albumin level of 1.8 g/dL. She was continued on 1800 kcalld of TPN with 24% of calories as protein through November 21, with intermittent spiking fevers (no source was identified). Hypomagnesemia developed ( 1.5 g/dL), but the remainder of the electrolytes and Ca, PO4 were all normal. The patient’s serum albumin level on November 22 was 2.0 g/dL. Her TPN was subsequently increased to 2200 kcal/d with 24% of that amount provided as protein ( 132 g/d), under the housestaff impression that her energy needs had not been met. On November 27 she became hypercapneic and tachycardic and was transferred to the SICU with ventilatory failure and atria1 fibrillation with a rapid ventricular response rate. Laboratory values at the time of transfer revealed: Na = 140 n-Q/L, K = 4.1 mEq/L, Cl = 105 mEq/L, HCOs = 25 mEq/L, blood urea nitrogen (BUN) = 29 mg/dL, Crt = 0.9 mg/dL, Glucose = 292 mg/dL, Ca = 7.9 mg/dL, PO, = 4.1, Mg = 2.1 mg/ dL, and Albumin = 2.6 g/dL. She subsequently underwent Swan-Ganz catheter placement with cardiac output = 4.5 L/ min, C.I. = 3.2 L * min-’ * m2 -I, SVR = 1400 dyne-set/cm-5, PA = 44126 mmHg, CVP = 21 mmHg, and PCWP = 22 mmHg. Arterial blood gases on 80% FI02 assist control ventilation (A/C) were pH 7.49, Paco2 = 35 mmHg, and Pa02 = 98 mmHg. She was started on broad-spectrum antibiotic coverage. Her subsequent hospital course was complicated by sepsis, congestive heart failure, and rapid ventricular-response atria1 fibrillation, which did not respond to a diltiazem drip (rate = 135 beats/mm). An echocardiogram revealed a normal left ventricular size, left ventricular hypokinesis, a mildly dilated left atrium, and moderate mitral and tricuspid regurgitation. She was started on digoxin without apparent response.

Intracoronary infusion of dilute ethanol for control of ventricular rate in patients with atrial fibrillation.

The effects of selective infusion of 25% ethanol into the AV nodal artery was assessed in 11 patients with atrial fibrillation and uncontrollably rapid ventricular response rates. The primary study objective was to achieve permanent modification of AV nodal function and control ventricular rate without drug therapy and without causing permanent complete AV block. "Clinical success" was defined as drug-free rate control by either AV nodal modification or the production of complete AV block. Selective catheterization and ethanol infusion into the AV nodal artery could be performed in nine patients. Intracoronary ethanol infusion acutely caused second- or third-degree AV nodal block in seven patients and an increase in AV nodal refractory period and Wenckebach cycle length in two patients. Acute occlusion of the AV nodal artery or infarction of nontarget myocardium was not observed. During follow-up of 22.2 +/- 2.2 months the primary study objective was attained in only four of nine patients treated, yielding an efficacy of 44%. However, the "clinical success" rate was 78%. The acute effects of ethanol on AV conduction did not predict the chronic effects. Selective intracoronary infusion of dilute ethanol to control the ventricular rate in atrial fibrillation should be considered when radiofrequency ablation has been unsuccessful. This method of chemical ablation is as effective and probably safer than rapid administration of 96% ethanol.

Longitudinal electrophysiologic assessment of asymptomatic patients with the Wolff-Parkinson-White electrocardiographic pattern.

Although most asymptomatic patients with the Wolff-Parkinson-White electrocardiographic pattern have a good prognosis, some die suddenly. The mechanism of sudden death is usually ventricular fibrillation, which is triggered by atrial fibrillation with a rapid ventricular response rate. Electrophysiologic testing has been proposed to identify asymptomatic patients who may be at risk for sudden death. Meaningful application of such testing requires a knowledge of whether the electrophysiologic measurements are reproducible over time. Consequently, we performed electrophysiologic studies on two occasions at least 36 months apart (mean +/- SD, 54.7 +/- 14) in 29 asymptomatic patients with the pattern. Twenty-seven patients remained asymptomatic, and sustained supraventricular tachycardia developed in two during the follow-up period. Nine patients (31 percent) lost the capacity for preexcitation and anterograde conduction over the accessory pathway, which produces the Wolff-Parkinson-White pattern. The others had little change in measurements of conduction over the accessory pathway. Patients who lost conduction over the accessory pathway tended to be older (mean +/- SD, 50 +/- 18 vs. 39 +/- 11 years; P = 0.06) than patients who retained preexcitation, and they had longer anterograde effective refractory periods at the first assessment (414 +/- 158 vs. 295 +/- 27 msec; P = 0.003). We conclude that a considerable number of asymptomatic patients with the Wolff-Parkinson-White pattern lose their capacity for anterograde conduction over the accessory pathway. This loss of capacity probably contributes to the low mortality among asymptomatic patients.

Chronic Rapid Atrial Pacing to Maintain Atrial Fibrillation: Use to Permit Control of Ventricular Rate in Order to Treat Tachycardia Induced Cardiomyopathy

LR was a patient, followed over a 16-year period, who presented with an atrial tachycardia which was initially intermittent, but became incessant. Neither the atrial tachycardia nor the associated rapid ventricular response rate could be treated successfully with available drug therapy, resulting in a dilated cardiomyopathy and New York Heart Association (NYHA) class III-IV congestive heart failure. Acute induction of atrial fibrillation with rapid atrial pacing demonstrated that the associated ventricular rate could be satisfactorily slowed with digitalis therapy. Initially, short bursts from an implanted, radiofrequency controlled, patient activated pacemaker programmed to a rate of 600 bpm and connected to a permanent endocardial atrial J lead successfully interrupted the tachycardia and precipitated atrial fibrillation. Over a period of 3 months, this therapy changed the patient's heart failure to NYHA class II status. Subsequently, precipitation of atrial fibrillation with this technique failed, resulting in return to NYHA class III-IV congestive heart failure. Therefore, a custom-designed, high rate, rate-programmable pacemaker was implanted to pace the atria rapidly and continuously to maintain atrial fibrillation. A pacing rate of 375 bpm plus digoxin slowed the ventricular rate to 70-80 bpm, with stabilization of the congestive heart failure to NYHA class II. The pacemaker generator was replaced 6 months later, and after another 5 months, pacing was discontinued. The patient's subsequent rhythm remained stable atrial fibrillation with clinically successful control of both the ventricular rate and heart failure (NYHA class II) until the patient's death 72 months later. This unique case demonstrates another form of chronic therapy which, in selected cases, can be used for the long term control of rapid ventricular response rates to supraventricular arrhythmia.

Use of constant-infusion verapamil for the treatment of postoperative supraventricular tachycardia.

The effects of constant-infusion verapamil were studied in ten postoperative ICU patients who developed supraventricular tachycardia (atrial fibrillation) with rapid ventricular response rates. A 5-mg iv bolus dose of verapamil was followed by a 5-mg/h infusion that continued for 8 h. Ventricular rates were significantly (p less than .005) reduced from a pretreatment mean of 156 +/- 14 (SD) to 104 +/- 9 beat/min on constant-infusion therapy. This therapy was well tolerated without observed side-effects. Moreover, constant-infusion verapamil might avoid the hypotension and wide range of ventricular rates frequently encountered with repeated bolus doses of verapamil.

Treatment of multifocal atrial tachycardia with verapamil.

MULTIFOCAL atrial tachycardia is a distinct electrocardiographic entity characterized by an atrial rate of more than 100 beats per minute, the presence of at least three different P-wave forms, and variation in the PR and PP intervals.1 The condition usually occurs episodically in the setting of an acute clinical decompensation in seriously ill patients, often in the respiratory intensive care unit, and it usually resolves with management of the underlying illness.2 However, as in any atrial tachyarrhythmia, a rapid ventricular response rate may lead to myocardial ischemia or heart failure, and thus the need to treat multifocal atrial tachycardia may . . .

Preexcitation Syndrome Presented with Ventricular Tachycardia - A Case Report

An adult unconscious patient was brought to intensive care unit (ICU) with impalpable peripheral pulse, non-recordable blood pressure (BP), gross pallor, cyanosis, sweating and gasping respiration along with very rapid and feeble carotid pulse. It revealed ventricular tachycardia on monitor and was revived successfully by immediate direct current (DC) cardioversion along with other resuscitative measures. There was no contributory past history. Subsequent electrocardiogram (ECG) on sinus rhythm was diagnosed as Wolff-Parkinson-White (WPW) syndrome, the most prominent manifestation of preexcitation syndrome, in which the most common tachyarrhythmia is atrio-ventricular reciprocating tachycardia (AVRT). It is classified as orthodromic (more common) or antidromic (less common). Antidromic AVRT is difficult to distinguish from ventricular tachycardia on ECG. Atrial flutter and fibrillation are less common but potentially more serious because they can result in rapid ventricular response rates and, in rare instances, ventricular fibrillation. However, any sustained symptomatic tachyarrhythmia warrants urgent resuscitative electrical and pharmacological maneuver and interventions to restore life, regarding which the health care providers should always remain familiar and updated by Continuing Medical Education (CME). Key words: Wolff-Parkinson-White syndrome, tachyzrrhythmia, preexicitation syndrome. DOI: 10.3329/jafmc.v5i2.4585 JAFMC Bangladesh Vol.5(2) (December) 2009, pp.46-48