Cardioneuroablation for the Treatment of Hypervagotonic Sinus Node Dysfunction.

Hypervagotonic sinus node dysfunction (SND) is a form of SND with sinus bradycardia caused by enhanced vagal tone. Indirect proof of hypervagotonia as the mechanism can be inferred from resolution of bradycardia following atropine infusion. In symptomatic patients, pacemaker implantation is recommended. We describe cardioneuroablation as a treatment for hypervagotonic SND.

Sinus Tachycardia: a Multidisciplinary Expert Focused Review.

Sinus tachycardia (ST) is ubiquitous, but its presence outside of normal physiological triggers in otherwise healthy individuals remains a commonly encountered phenomenon in medical practice. In many cases, ST can be readily explained by a current medical condition that precipitates an increase in the sinus rate, but ST at rest without physiological triggers may also represent a spectrum of normal. In other cases, ST may not have an easily explainable cause but may represent serious underlying pathology and can be associated with intolerable symptoms. The classification of ST, consideration of possible etiologies, as well as the decisions of when and how to intervene can be difficult. ST can be classified as secondary to a specific, usually treatable, medical condition (eg, pulmonary embolism, anemia, infection, or hyperthyroidism) or be related to several incompletely defined conditions (eg, inappropriate ST, postural tachycardia syndrome, mast cell disorder, or post-COVID syndrome). While cardiologists and cardiac electrophysiologists often evaluate patients with symptoms associated with persistent or paroxysmal ST, an optimal approach remains uncertain. Due to the many possible conditions associated with ST, and an overlap in medical specialists who see these patients, the inclusion of experts in different fields is essential for a more comprehensive understanding. This article is unique in that it was composed by international experts in Neurology, Psychology, Autonomic Medicine, Allergy and Immunology, Exercise Physiology, Pulmonology and Critical Care Medicine, Endocrinology, Cardiology, and Cardiac Electrophysiology in the hope that it will facilitate a more complete understanding and thereby result in the better care of patients with ST.

Dyspnea in Chronic Low Ventricular Preload States.

Dyspnea in low-preload states is an underrecognized but growing diagnosis in patients with unexplained dyspnea. Patients can often experience debilitating symptoms at rest and with exertion, as low measured preload often leads to decreased cardiac output and ultimately dyspnea. In the present article, we performed a review of the literature and a multidisciplinary evaluation to understand the pathophysiology, diagnosis, and treatment of dyspnea in low-preload states. We explored selected etiologies and suggested an algorithm to approach unexplained dyspnea. The mainstay of diagnosis remains as invasive cardiopulmonary exercise testing. We concluded with a variety of nonpharmacological and pharmacological therapies, highlighting that a multifactorial approach may lead to the best results.

COVID-19 and postural tachycardia syndrome: a case series.

BACKGROUND: Postural tachycardia syndrome (PTS) is a novel identified sequela of COVID-19 infection. This observational study describes clinical presentation, testing, and treatment response in seven patients diagnosed with PTS following COVID-19 infection. CASE SUMMARY: A total of seven active patients (three collegiate athletes, one recreational athlete, two registered nurses, one hospitality employee), age 24 ± 6 years, and six females were followed for a mean of 152 ± 105 days after contracting COVID-19. Tilt table was performed to establish the diagnosis. The most common presenting symptoms were palpitations (7/7), dyspnoea (6/7), and gastrointestinal complaints (5/7). One patient required hospitalization for symptom management. The mean latency of PTS onset following COVID-19 was 21 ± 15 days. Electrocardiograms (ECGs) demonstrated sinus rhythm in all patients, one with resting sinus tachycardia. Echocardiogram demonstrated normal systolic and diastolic left ventricular function in all patients. On tilt table testing, baseline heart rate (HR) was 72 ± 12 with maximum HR reaching 136 ± 13. Six of seven patients failed to respond to supportive therapy alone, and two patients failed medical management with ivabradine, midodrine, and/or metoprolol. Of three severely symptomatic patients, two demonstrated some degree of clinical recovery with intravenous immunoglobulin (IVIG). DISCUSSION: This novel case series describes the development of PTS in the context of COVID-19 infection. Severity of symptoms and response to treatment was heterogeneous. Interestingly, patients were poorly responsive to traditional PTS treatments, but IVIG showed potential as a possible therapeutic strategy for refractory PTS in two patients, particularly following COVID-19 infection.

Functional capacity and quality of life in the postural tachycardia syndrome: A retrospective cross-sectional study.

BACKGROUND: Postural tachycardia syndrome (POTS) is a complex syndrome of orthostatic intolerance that significantly affects quality of life. The relationship between functional capacity, quality of life, and age remains poorly understood in this patient population. The purpose of this cross-sectional study was to assess the clinical and exercise characteristics of patients with POTS who underwent exercise stress testing as part of cardiac rehabilitation, and to evaluate the relationships between functional capacity with age and sex, as well as the relationship between functional capacity and quality of life. METHODS: We included 255 consecutive adult patients with the diagnosis of POTS, by tilt table testing, who underwent exercise stress testing between 2012 and 2017. Clinical and stress test data were obtained from electronic medical records. RESULTS: Of the 255 patients, 232 (91%) were women, with median age 33.5 years. Prevalence of traditional CAD risk factors was low (2% diabetes, 13% hypertension, 7% hyperlipidemia, and 26% smoking history). Mean resting BP was 114 ± 13 mmHg systolic, resting HR was 76 ± 13 bpm, METs achieved 9.2 ± 2.2, and 1 min HR recovery 32 ± 17 bpm. 113 patients (44%) had abnormal functional capacity for age and sex. When analyzed by age groups, younger POTS patients had increasingly lower than expected functional capacity (compared to predicted normals) than did older patients (ANOVA P = 0.0017). The SF-36 physical component of patients with abnormal functional capacity was significantly lower than those with normal functional capacity. (p = 0.006). CONCLUSIONS: In this large cohort, patients with POTS were predominantly female (91%) and relatively young. The novel findings are that younger patients with POTS were more likely to have lower-than-average functional capacity for their age and sex compared to older patients, and that abnormal functional capacity was associated with lower quality of life by SF-36 physical component.

Proarrhythmic effects from competitive atrial pacing and potential programming solutions.

BACKGROUND: Programmed long AV delays and intrinsic long first degree AV block may increase risk for competitive atrial pacing (CAP) in devices without CAP avoidance algorithms. METHODS: Patients identified with CAP-induced mode switch episodes were followed clinically from September 2013 to August 2019. Attempts to avoid CAP included shortening of postventricular atrial refractory period (PVARP) or postventricular atrial blanking period (PVAB), or change to AAI or DDI modes. After observing associations with sensor-driven pacing, rate response was inactivated in a subset. RESULTS: Among 23 patients identified with CAP (22 St Jude Medical [Abbott]; one Boston Scientific Corporation devices), atrial fibrillation (AF) was induced in 12 (52%), lasting 10 seconds to 28 hours and 32 minutes. In one patient with an ICD CAP-induced AF with rapid ventricular rates that triggered a shock, inducing ventricular fibrillation, syncope, and another shock. Changing AV delays and shortening of PVARP failed to resolve CAP. After noting that all had CAP during sensor-driven pacing, rate response was inactivated in seven, resolving further device-induced AF in the three of seven that had prior CAP-induced AF. In two patients with intact AV conduction, AAI(R) pacing resolved further documentation of CAP. CONCLUSIONS: CAP predominantly occurs during sensor-driven atrial pacing that competes with intrinsic atrial events falling in PVARP. Inactivation of the activity sensor or change to atrial-based pacing modes (AAI/R) appears to effectively prevent induction of device-induced atrial proarrhythmia. Ultimately, a corrective algorithm is needed to avoid CAP-induced proarrhythmia.

High Submaximal Exercise Heart Rate Impacts Exercise Intolerance in the Postural Orthostatic Tachycardia Syndrome.

PURPOSE: Exercise intolerance is a hallmark of the postural orthostatic tachycardia syndrome (POTS). However, no data are available on the implications of an exaggerated submaximal heart rate (HR) on exercise intolerance in patients. We investigated whether exaggerated HR responses occurring early on during incremental stress testing relate with increased odds of POTS and exercise intolerance. METHODS: Clinical characteristics and stress test HRs were compared between adults with POTS achieving ≥85% predicted metabolic equivalents (METs) (EX-TL, n = 101; body mass index [BMI] 24 ± 5 kg·m; 95% women) or <85% (EX-INTL, n = 71; BMI 28 ± 7 kg·m; 79% women) and sedentary controls (n = 30; BMI 36 ± 3 kg·m; 87% women). Multivariate logistic regressions were performed to estimate ORs and the probability of POTS and exercise intolerance associated with exercise HRs. RESULTS: Exercise tolerance was increased in EX-TL, but not in EX-INTL (10.0 ± 1.3 and 8.3 ± 1.5 METs vs 8.0 ± 1.6 METs, respectively) versus controls. Absolute peak HR was increased in EX-TL and EX-INTL versus controls (P < .01), whereas percent predicted did not differ. Exercise within the first-to-second stress stages was performed at exaggerated HRs (122 ± 17 bpm vs 103 ± 15 and 113 ± 15 bpm, P < .001) and percent HR reserve in EX-INTL versus controls and EX-TL (49% ± 12% vs 34% ± 11% and 41% ± 11%, P < .001), respectively. In multivariate analyses, peak HR was not significant, whereas increased submaximal HR (either variable) was associated with increased odds of EX-TL or EX-INTL. Lastly, odds of EX-INTL increased as METs decreased, whereas METs was not a predictor of EX-TL. CONCLUSIONS: An exaggerated submaximal exercise HR is predictive of POTS and exercise intolerance, and this chronotropic phenotype is exacerbated in patients achieving <85% predicted METs.

Correction to: ST­segment changes during tilt table testing for postural tachycardia syndrome: correlation with exercise stress test results.

Unfortunately, the 3rd author name was incorrectly published in the original publication. The complete correct name is given below.

ST-segment changes during tilt table testing for postural tachycardia syndrome: correlation with exercise stress test results.

BACKGROUND: Prior studies have reported ECG (Electrocardiogram) changes during tilt table testing (TTT), specifically during repolarization with ST-segment and T-wave changes. The correlation with ischemic evaluation remains unclear. The purpose of this study was to analyze the prevalence of ST-segment changes during TTT in a young, otherwise healthy population of patients with postural tachycardia syndrome (POTS), and correlate them with exercise stress test results. METHODS: Two hundred and fifty-five patients with POTS who underwent TTT and an exercise treadmill test (ETT) were analyzed. RESULTS: Forty-five had ST-segment changes/depressions during TTT (91% female, average age 36 years). Of the 45, three had ST-segment depression during ETT; all three had negative exercise stress echocardiograms (ESEs). Two others had ST-segment depressions on ETT (but not TTT), with negative ESEs. CONCLUSION: In a cohort of young, female, otherwise healthy patients with POTS, ST-segment changes occurred in a significant portion (18%) of patients during TTT. When evaluated with exercise stress testing, these patients had no evidence of underlying ischemia on ETT or ESE.

Postural Tachycardia Syndrome and Vasovagal Syncope: A Hidden Case of Obstructive Cardiomyopathy without Severe Septal Hypertrophy.

A 36-year-old female with symptoms of orthostatic intolerance and syncope was diagnosed with vasovagal syncope on a tilt table test and with postural tachycardia syndrome (POTS) after a repeat tilt table test. However, an echocardiogram at our institution revealed obstructive cardiomyopathy without severe septal hypertrophy, with a striking increase in left ventricular outflow tract gradient from 7 mmHg at rest to 75 mmHg during Valsalva, with a septal thickness of only 1.3 cm. Cardiac MRI showed an apically displaced multiheaded posteromedial papillary muscle with suggestion of aberrant chordal attachments to the anterior mitral leaflet contributing to systolic anterior motion of the mitral valve. She underwent surgery with reorientation of the posterior medial papillary muscle head, resection of the tethering secondary chordae to the A1 segment of the mitral valve, chordal shortening and tacking of the chordae to the A1 and A2 segments of the mitral valve, and gentle septal myectomy. After surgery, she had significant improvement in her prior symptoms. To our knowledge, this is the first reported case of obstructive cardiomyopathy without severe septal hypertrophy with abnormalities in papillary muscle and chordal attachment, in a patient diagnosed with vasovagal syncope and POTS.

Compound heterozygous mutations in the SCN5A-encoded Nav1.5 cardiac sodium channel resulting in atrial standstill and His-Purkinje system disease.

An 11-year-old girl on evaluation for syncope was found to have progressive sinus node dysfunction and His-Purkinje system disease with atrial standstill. Genetic analysis revealed compound heterozygous mutations of the SCN5A gene in a novel combination.

Characteristics of heart rate reduction with resumption of supine position in the postural tachycardia syndrome: factors influencing recovery.

OBJECTIVES: Postural orthostatic tachycardia syndrome (POTS), a heart rate (HR) rise with upright positioning, is dependent on autonomic influences. HR recovery (HR decrease after exercise cessation) is a measure of autonomic function. Characteristics of HR reduction during supine Recovery after head-up Tilt in POTS patients have not been elucidated. METHODS: 113 subjects (mean age 41.7 years, 86 female), diagnosed with POTS on head-up Tilt were analyzed. HR's were recorded during baseline supine position, 70-degree Tilt, and 20 sec, 1 min and 2 min of supine Recovery. Percent HR reduction during Recovery was calculated. RESULTS: Baseline HR was 68.7±13.4 bpm. Maximum HR during Tilt was 109±16.9 bpm. Mean HR was 84.2±20 bpm at 20 sec, 78.5±18.9 bpm at 1-min, and 77.1±18.3 bpm at 2 min of Recovery. Younger age and slower baseline HR were associated with greater HR reductions at 20 sec (p=0.006, p=0.000, respectively). Younger age, slower baseline HR and less time to achieve POTS were associated with greater HR reductions at 1 min (p=0.025, p=0.000, p=0.000, respectively) and at 2 min (p=0.004, p=0.000, p=0.000, respectively). Gender and baseline blood pressures were not significant. CONCLUSIONS: In POTS patients, HR quickly decreases upon resuming supine position. Younger age, slower baseline HR and less time to achieve POTS were associated with greater HR reductions during supine Recovery. Further study is needed to determine mechanisms, as well as analyze differences in symptoms or prognosis.

POTS due to excessive venous pooling in an enlarged inferior vena cava.

Postural tachycardia syndrome (POTS) is a form of orthostatic intolerance characterized by a marked increase in heart rate within the first 10 min of head-up tilt (HUT). We present a patient whose enlarged inferior vena cava that appears to be a contributing mechanism to her POTS and presyncopal symptoms.

Circadian and gender effects on repolarization in healthy adults: a study using harmonic regression analysis.

BACKGROUND: Sudden cardiac death and myocardial infarction have a circadian variation with a peak incidence in the early morning hours. Increased dispersion of repolarization facilitates the development of conduction delay necessary to induce sustained arrhythmia. Both QT-dispersion and T-wave peak to T-wave end (TpTe) have been proposed as markers of dispersion of myocardial repolarization. METHODS: Forty healthy adults (20 women), age 35-67 years old, with normal EKGs, echocardiograms, stress tests, and tilt-table tests were analyzed during a 27-hour hospital stay. EKGs were done at eight different time points. QT-intervals, QT-dispersion, and TpTe were measured at each time point. Harmonic regression was used to model circadian periodicity, P < 0.05 was considered significant. RESULTS: The composite QT-interval was longer in women than in men (416 + or - 17 msec vs 411 + or - 20 msec, respectively, P = 0.006). The QT-dispersion among all leads was greater in men than women (37 + or - 13 msec vs 30 + or - 11 msec, respectively, P < 0.0001); a similar difference was found in the precordial leads. Harmonic regression showed that QT-dispersion had a significant circadian variation, primarily in men. In men, the maximum QT-dispersion occurred at 6 AM (45 + or - 15 msec). TpTe also had a significant circadian variation that was not affected by gender in the majority of leads. CONCLUSIONS: A circadian variation exists in the dispersion of myocardial repolarization, as measured by both TpTe and QT-dispersion. Men and women have a different circadian variation pattern. Further studies regarding the mechanisms and clinical implications are needed.

Early versus late postural tachycardia: a re-evaluation of a syndrome.

Postural tachycardia syndrome (POTS) involves an HR-rise within 10 minutes of head-up tilt. Hypokinetic circulation, older age, and ACE-inhibitor or Angiotensin-Receptor Blockers were associated with "Late" POTS (after 10 minutes of tilt) versus "Early" POTS (within 10 minutes of tilt).