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.

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).

Dynamic changes in T-wave amplitude during tilt table testing: correlation with outcomes.

BACKGROUND: Changes in autonomic tone may play a role in syncope. Autonomic tone has been shown to affect cardiac repolarization in the ECG. Changes in the T wave can be seen during head-up tilt table (HUT) testing with unknown significance or relationship to outcomes. METHODS: Twelve-lead ECGs during HUT testing from 150 patients were reviewed from a prospectively collected registry database. ECGs during supine-rest, 30-45-70 degrees tilt, and 5-minute supine recovery were reviewed. Changes in the T wave, that is, decreased amplitude with or without becoming negative or flipping from negative to positive, were recorded for each stage. Outcomes of the HUT test include nondiagnostic, postural orthostatic hypotension (POH), postural orthostatic tachycardia syndrome (POTS), and vasovagal response (VVR). Age (Younger: <50 year old; Older: > or = 50 year old) and gender were analyzed. RESULTS: Of 150 patients (108 women; 80 Younger), 135 had T-wave changes during HUT; changes resolved in 114 patients during supine recovery. Changes mostly occurred in inferior and anterolateral leads. POH occurred in 114 patients, POTS in 67, and VVR in 30. T-wave changes in V1 inversely correlated with POH (P = 0.005). T-wave changes in inferior leads II, III, aVF and in anterolateral leads V3-V6 positively correlated with POTS (P < 0.05). Female gender and younger age correlated with POTS independent of the leads (P < 0.05). Concomitant T-wave changes in V5 and V6 correlated with VVR; changes in aVF also correlated with VVR (P < 0.05). CONCLUSIONS: Dynamic T-wave changes during HUT testing in inferior and anterolateral leads are associated with POTS and VVR independent of age and gender. Changes in autonomic tone may play a role and need further study.

Age and gender difference in ST height at rest and after double autonomic blockade in normal adults.

BACKGROUND: ST elevation is commonly seen in young, healthy men. The exact mechanisms that cause ST height to be greater in young men are not yet completely understood. The purpose of the present study was to determine whether autonomic tone is responsible for age and gender differences in ST height. METHODS: Gender and age differences in ST height were studied at rest and after double autonomic blockade (DAB) with atropine and propranolol. Fifty healthy men and women were included (16 men, 14 women, age 23-32 years; 9 men, 11 women, age 65-79 years). Twelve-lead ECGs were registered at rest and after DAB. Leads II and V(1)-V(4) were chosen for analysis. ST height (in mm) was measured manually at the J-point, and 40 ms and 80 ms after the J-point. Values were corrected for QRS amplitude. RESULTS: Gender and age differences in ST height were seen in both rest and DAB data. Men had greater ST height compared to women at J-point, 40 and 80 ms after the J-point (P < or = 0.0001), and younger subjects had greater ST height than older subjects at J-point (P = 0.0140), 40 and 80 ms after the J-point (P < or = 0.0001). DAB did not change ST height at J-point or at 40 ms, but increased ST height at 80 ms. Women had less of an increase in ST height following DAB than men did. CONCLUSIONS: ST elevation in the absence of structural or electrical heart disease is mainly seen in young men. Age and gender difference persist after DAB and thus are not due to differences in autonomic tone.

Quality of anastomosis in conventional on-pump coronary artery bypass graft surgery: influence of the interrupted technique using u-clips and correlation with intraoperative graft flow patterns.

BACKGROUND: The interrupted suture technique in creating graft-coronary artery anastomoses in coronary artery bypass graft (CABG) surgery is hypothesized to be superior to the standard continuous technique. However, because of the increased time and knot tying involved with the interrupted technique, the continuous suture became standard. In 2000, the U-clip (a self-closing metal clip) was introduced to help in creating an interrupted anastomosis, although data regarding its clinical use are still somewhat limited. Intraop-erative transit-time flow measurement (TTFM) of blood flow through an anastomosis is frequently used to assess quality of anastomosis creation; mean flow and pulsatile index (PI) are analyzed. PI should typically be between 1 and 5; higher values are associated with errors of anastomosis creation. The current study analyzes the difference in TTFM between U-clips and standard suture in CABG surgery. METHODS: The study population consists of 30 prospectively enrolled patients undergoing first-time on-pump conventional CABG surgery at St. Anthony Medical Center who were randomized to have their anastomosis created with either U-clips or suture. TTFM were recorded for left internal mammary artery to left anterior descending artery (LIMA-LAD) anastomoses. RESULTS: Of the 30 subjects enrolled (10 women), 12 operations were done with U-clips and 18 with suture. Body mass index (BMI) in the 2 groups was similar. In terms of mean flow, there was no difference between the 2 groups (29.8 +/- 18.4 mL/min for U-clips versus 26.6 +/- 11.0 mL/min for suture, P = .57). In terms of PI, again no difference was found (3.1 +/- 1.3 for U-clips versus 2.5 +/- 0.8 for suture, P = .12). CONCLUSIONS: The findings of this study suggest that U-clips are comparable to the standard suture for LIMA-LAD anastomoses in conventional on-pump CABG surgery in terms of intraoperative assessment of graft flow.