An unusual ECG deflection: Fact or artifact?

Peculiar electrocardiographic findings are not unusual and upon careful review can often be clarified. We present a case of an 85year-old woman with no previous cardiac history, incidentally discovered high grade atrioventricular block, and a puzzling electrocardiographic complex of unclear etiology which defies reasonable physiological explanations. The finding resembled a tiny QRS in a perfectly regular R-R interval following only non-conducted P-waves. The patient declined further work-up, so a definite cause could not be determined, but based on history, complex morphology, and inability to reproduce or explain the findings, we were compelled to accept the finding as an artifact.

The potential role of nonpharmacologic electrophysiology-based interventions in improving outcomes in patients hospitalized for heart failure.

Hospitalization for heart failure (HHF) is commonly associated with symptomatic improvement in response to standard medical therapy, yet there remains a substantial risk of rehospitalization and death. Clinically stable outpatients and decompensated inpatients represent two types of patients with chronic heart failure. In the former, treatment of common heart rhythm disorders with nonpharmacologic electrophysiology-based interventions is of substantial benefit in select patients. The potential benefits of these interventions in the hospitalized setting are not well studied. In this review, current knowledge is discussed and future research directions are suggested with nonpharmacologic electrophysiology-based interventions to reduce the morbidity and mortality associated with patients with HHF.

Recovery of heart rate variability and ventricular repolarization indices following exercise.

BACKGROUND: There is a heightened risk of sudden cardiac death related to exercise and the postexercise recovery period, but the precise mechanism is unknown. We have demonstrated that sympathoexcitation persists for ≥45 minutes after exercise in normals and subjects with coronary artery disease (CAD). The purpose of this study is to determine whether this persistent sympathoexcitation is associated with persistent heart rate variability (HRV) and ventricular repolarization changes in the postexercise recovery period. METHODS AND RESULTS: Twenty control subjects (age 50.7 ± 1.4 years), 68 subjects (age 58.2 ± 1.5 years) with CAD and preserved left ventricular ejection fraction (LVEF), and 18 subjects (age 57.6 ± 2.4 years) with CAD and depressed LVEF underwent a 16-minute submaximal bicycle exercise protocol with continuous ECG monitoring. QT and RR intervals were measured in recovery to calculate the time dependent corrected QT intervals (QTc), the QT-RR relationship, and HRV. QTc was dependent on the choice of rate correction formula. There were no differences in QT-RR slopes among the three groups in early recovery. HRV recovered quickly in controls, more slowly in those with CAD-preserved LVEF, and to a lesser extent in those with CAD-depressed LVEF. CONCLUSION: Despite persistent sympathoexcitation for the 45-minute recovery period, ventricular repolarization changes do not persist for that long and HRV changes differ by group. Additional understanding of the dynamic changes in cardiac parameters after exercise is needed to explore the mechanism of increased sudden cardiac death risk at this time.

Persistent sympathoexcitation long after submaximal exercise in subjects with and without coronary artery disease.

There is an increased risk of cardiac events after exercise, which may, in part, be mediated by the sympathoexcitation that accompanies exercise. The duration and extent of this sympathoexcitation following moderate exercise is unknown, particularly in those with coronary artery disease (CAD). Twenty control subjects (mean age, 51 years) and 89 subjects with CAD (mean age, 58 years) underwent two 16-min bicycle exercise sessions followed by 30-45 min of recovery. Session 1 was performed under physiological conditions to peak workloads of 50-100 W. In session 2, parasympathetic blockade with atropine (0.04 mg/kg) was achieved at end exercise at the same workload as session 1. RR interval was continually recorded, and plasma catecholamines were measured at rest and selected times during exercise and recovery. Parasympathetic effect, measured as the difference in RR interval with and without atropine, did not differ between controls and CAD subjects in recovery. At 30 and 45 min of recovery, RR intervals were 12% and 9%, respectively, shorter than at rest. At 30 and 45 min of recovery, plasma norepinephrine levels were 15% and 12%, respectively, higher than at rest. A brief period of moderate exercise is associated with a prolonged period of sympathoexcitation extending >45 min into recovery and is quantitatively similar among control subjects and subjects with CAD, with or without left ventricular dysfunction. Parasympathetic reactivation occurs early after exercise and is also surprisingly quantitatively similar in controls and subjects with CAD. The role of these autonomic changes in precipitating cardiac events requires further evaluation.

Strategies for pacemaker programming in acute heart failure.

In the past decade, cardiac pacing devices (either permanent pacemakers or Implanted Cardioverter Defibrillators) have become increasingly common in patients with heart failure. The manner in which the device is programmed to pace the heart can have significant implications on cardiac hemodynamics, both positive and negative. As such, in patients hospitalized with acute heart failure who have cardiac pacing devices, the clinician should note whether the programming of the device could be contributing to the patient's symptoms, and whether further programming changes could be made to improve the patient's clinical status. As of this date, there are no consensus guidelines available for the management of pacemaker programming in acute heart failure. This review article will discuss the physiologic implications of several parameters of pacemaker programming on heart failure, including the degree of RV pacing, the programmed atrioventricular (AV) interval, and the programmed interventricular pacing delay in patients with cardiac resynchronization therapy (CRT) devices. Based on the available data on the above parameters, this article will then propose a general algorithmic approach to the evaluation and management of patients with pacing devices who are hospitalized with acute heart failure.

Rapid Exclusion of COVID Infection With the Artificial Intelligence Electrocardiogram.

OBJECTIVE: To rapidly exclude severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection using artificial intelligence applied to the electrocardiogram (ECG). METHODS: A global, volunteer consortium from 4 continents identified patients with ECGs obtained around the time of polymerase chain reaction-confirmed COVID-19 diagnosis and age- and sex-matched controls from the same sites. Clinical characteristics, polymerase chain reaction results, and raw electrocardiographic data were collected. A convolutional neural network was trained using 26,153 ECGs (33.2% COVID positive), validated with 3826 ECGs (33.3% positive), and tested on 7870 ECGs not included in other sets (32.7% positive). Performance under different prevalence values was tested by adding control ECGs from a single high-volume site. RESULTS: The area under the curve for detection of acute COVID-19 infection in the test group was 0.767 (95% CI, 0.756 to 0.778; sensitivity, 98%; specificity, 10%; positive predictive value, 37%; negative predictive value, 91%). To more accurately reflect a real-world population, 50,905 normal controls were added to adjust the COVID prevalence to approximately 5% (2657/58,555), resulting in an area under the curve of 0.780 (95% CI, 0.771 to 0.790) with a specificity of 12.1% and a negative predictive value of 99.2%. CONCLUSION: Infection with SARS-CoV-2 results in electrocardiographic changes that permit the artificial intelligence-enhanced ECG to be used as a rapid screening test with a high negative predictive value (99.2%). This may permit the development of electrocardiography-based tools to rapidly screen individuals for pandemic control.

Diffuse B Cell Lymphoma Leading to Complete Heart Block: Is This Transient or Permanent?

BACKGROUND Cardiac lymphomas can lead to heart block through tumor disruption of the cardiac conduction system. It is reported that with cardiac tumor treatment, conduction abnormalities can resolve. We present a case of cardiac lymphoma resulting in complete heart block requiring a pacemaker, followed by reduction of the pacing burden after chemotherapy. CASE REPORT A 72-year-old woman with a medical history of hypertension, hypothyroidism, and persistent atrial fibrillation presented with dyspnea on exertion and fatigue for 2 weeks. Electrocardiography revealed complete heart block with junctional bradycardia of 48 beats per min. Transthoracic echocardiography demonstrated preserved left ventricular systolic function along with a large mass (3.6×3.7 cm). An endomyocardial biopsy was consistent with diffuse large B cell lymphoma, and the cardiac involvement was thought to be secondary based on positron emission tomography scan findings. Her clinical course was complicated by an episode of syncope deemed to be due to transient asystole, and an urgent single-chamber permanent pacemaker was implanted. Chemotherapy was initiated with R-CHOP, and, following the second cycle of chemotherapy, a positron emission tomography scan revealed no increased radiotracer uptake and thus resolution of all tumors. An echocardiogram 6 weeks after chemotherapy showed complete resolution of the cardiac mass. Subsequent serial pacemaker checks demonstrated improvement of atrioventricular nodal function as manifested by reduced pacing burden. CONCLUSIONS Lymphoma with cardiac involvement can lead to conduction abnormalities, including CHB, and heart block in the setting of these tumors may be reversible with appropriate therapy; however, implantation of a pacemaker remains inevitable is some cases.

Reflections on the early invasive clinical cardiac electrophysiology era through fifty manuscripts: 1967-1992.

In 1967, researchers in The Netherlands and France independently reported a new technique, later called programmed electrical stimulation. The ability to reproducibly initiate and terminate arrhythmias heralded the beginning of invasive clinical cardiac electrophysiology as a medical discipline. Over the next fifty years, insights into the pathophysiologic basis of arrhythmias would transform the field into an interventional specialty with a tremendous armamentarium of procedures. In 2015, the variety and complexity of these procedures were major reasons that led to the recommendation for an increase in the training period from one year to two years. The purpose of this manuscript is to present fifty manuscripts from the early invasive clinical cardiac electrophysiology era, between 1967 and 1992, to serve as an educational resource for current and future electrophysiologists. It is our hope that reflection on the transition from a predominantly noninvasive discipline to one where procedures are commonly utilized will lead to more thoughtful patient care today and to inspiration for innovation tomorrow. In the words of the late Dr. Mark E. Josephson, "It is only by getting back to the basics that the field of electrophysiology will continue to grow instead of stagnate."

Fluoroscopic investigation of Riata® transvenous defibrillator leads.

BACKGROUND: Implantable cardioverter-defibrillator leads from Riata® family (St. Jude Medical Inc., Sylmar, CA, USA) have been recently recalled by Food and Drug Administration for concerns of a unique type of "inside-out" insulation failure leading to conductor externalization. The objective of this study was to evaluate the prevalence and predictors of conductor externalization in patients implanted with Riata 8 French (Fr) and 7 Fr leads. METHODS: Patients implanted with Riata® and Riata ST® who were actively followed up in our institution were scheduled for high resolution 3 view fluoroscopy and device interrogation including high voltage (HV) lead impedance testing. Fluoroscopic images were graded as presence of externalization or no externalization. RESULTS: Of the 90 patients who underwent screening fluoroscopy, majority had dual coil leads (62.5%) and median duration from the implant time to screening was 79.5 months. Twenty four (26.7%) patients exhibited evidence of lead externalization with 10 (41.6%) of these showing electrical abnormalities at the time of screening. No externalization was seen in the 7 Fr leads. Pacing thresholds were significantly elevated in the externalized cohort compared to non-externalized group (1.42 ± 1.23 vs. 0.93 ± 0.53; p = 0.01). Time since lead implant and lead diameter emerged as significant predictors of lead externalization on univariate analysis with only lead diameter being significant on multivariate analysis (odds ratio 30.68; 4.95-∞, p = 0.001). CONCLUSIONS: Prevalence of insulation failure exhibiting as conductor externalization is high (26.7%) among the large diameter 8 Fr Riata® leads with a significant proportion of patients manifesting electrical failure. High resolution 3 view fluoroscopy is a reasonable approach to screen for this unique type of insulation failure.

Effect of race on the frequency of postoperative atrial fibrillation following coronary artery bypass grafting.

Atrial fibrillation (AF) commonly complicates the postoperative course after coronary artery bypass grafting (CABG). Among the general population, African Americans have been shown to have a lower prevalence of AF than European Americans. Although many factors have been identified to predict risk for postoperative AF, race has not been examined. All patients aged ≥18 years who underwent CABG at Henry Ford Hospital during a 5-year period from January 1, 2004, to December 31, 2008, were included. Patients were excluded for any previous diagnosis of AF or if they had concomitant valve surgery at the time of CABG. The incidence of AF was determined by International Classification of Diseases, Ninth Revision, coding from postoperative hospitalization records. Overall, 1,001 patients were eligible for analysis. Of these, 731 (73%) were European American and 270 (27%) were African American. The African American group had a higher prevalence of hypertension (75.6% vs 58.8%, p <0.001) and heart failure (22.6% vs 15.7%, p = 0.01) and a trend toward a higher prevalence of diabetes mellitus (38.1% vs 33.4%, p = 0.159). Postoperative AF was diagnosed in 214 European Americans (29.3%) and 50 African Americans (18.5%) (p = 0.001). In multivariate analysis adjusting for age strata, gender, hypertension, diabetes, and heart failure, African Americans had less postoperative AF than European Americans, with an adjusted odds ratio of 0.539 (95% confidence interval 0.374 to 0.777, p = 0.001). In conclusion, African Americans have a significantly reduced incidence of AF compared to European Americans after CABG.

Autonomic effects of exercise-based cardiac rehabilitation.

PURPOSE: One hypothesis by which exercise-based cardiac rehabilitation (CR) reduces mortality and cardiac events in patients with coronary artery disease invokes a beneficial effect of exercise on autonomic modulation. This study aimed to evaluate the autonomic effects of CR in patients with coronary artery disease. METHODS: Participants referred to phase 2 CR underwent 4 bicycle stress tests, 2 before starting CR and 2 after. On visits 1 and 3, a symptom-limited bicycle stress test was performed. On visits 2 and 4, the subject exercised to the same workload, but atropine was administered during maximal exercise to achieve parasympathetic blockade. Parasympathetic effect in exercise recovery was computed before and after CR. Heart rate variability for each segment was also quantified. Plasma catecholamine levels were obtained at baseline, peak exercise, and during recovery. RESULTS: Seventeen subjects (age 56 ± 10 years; 4 women) were enrolled. Six completed the post-CR testing. There was a significant increase in parasympathetic effect during exercise recovery post-CR (P < .001). There was also a significant increase in heart rate variability during exercise recovery post-CR (P < .001). Resting catecholamine levels were not different pre- and post-CR (NS). Post-CR, there was a blunted increase in peak exercise plasma catecholamine levels compared with those seen pre-CR, but this was not statistically significant. CONCLUSIONS: We demonstrated a shift toward increased parasympathetic and possibly, blunted sympathetic effect in this cohort after completion of an exercise-based CR program. Our findings provide insight into the mechanism for the observed changes in exercise parameters following exercise training, and the improved outcomes seen after CR.

Assessment of autonomic function in cardiovascular disease: physiological basis and prognostic implications.

Certain abnormalities of autonomic function in the setting of structural cardiovascular disease have been associated with an adverse prognosis. Various markers of autonomic activity have received increased attention as methods for identifying patients at risk for sudden death. Both the sympathetic and the parasympathetic limbs can be characterized by tonic levels of activity, which are modulated by, and respond reflexively to, physiological changes. Heart rate provides an index of the net effects of autonomic tone on the sinus node, and carries prognostic significance. Heart rate variability, though related to heart rate, assesses modulation of autonomic control of heart rate and carries additional prognostic information, which in some cases is more powerful than heart rate alone. Heart rate recovery after exercise represents the changes in autonomic tone that occur immediately after cessation of exercise. This index has also been shown to have prognostic significance. Autonomic evaluation during exercise and recovery may be important prognostically, because these are high-risk periods for sudden death, and the autonomic changes that occur with exercise could modulate this high risk. These markers provide related, but not redundant information about different aspects of autonomic effects on the sinus node.