OBJECTIVE: Immune checkpoint inhibitor (ICI)-associated myocarditis, particularly severe ICI-associated myocarditis, has a high mortality rate. However, the predictive value of electrocardiogram (ECG) remains unclear. The present study aimed to evaluate the predictive value of clinical and electrocardiographic parameters for severe myocarditis.
METHODS: Clinical and electrocardiographic data of 73 cancer patients with ICI-associated myocarditis were retrospectively collected. The severity of ICI-associated myocarditis was graded using the NCCN guidelines for managing immunotherapy-related toxicities. Myocarditis grades 1-2 and grades 3-4 were classified as mild and severe myocarditis, respectively. Logistic regression analysis was performed to analyze the predictive value of each parameter in predicting severe myocarditis.
RESULTS: Among the 73 patients with myocarditis, 20 (27.4%) patients had severe myocarditis. Compared with mild myocarditis group, sinus tachycardia (p = 0.001), QRS duration ≥110 ms (p = 0.001), prolonged QTc interval (p < 0.001), and bundle branch block (p = 0.007) at the time of myocarditis were more common in the severe myocarditis group. Logistic regression analysis revealed that sinus tachycardia (p = 0.028) and QTc interval prolongation (p = 0.007) were predictors of severe myocarditis. Whereas the predictive value of other electrocardiographic parameters was weak. Concurrent targeted therapy didn\'t increase the risk of severe myocarditis. A high NT-proBNP level was associated with severe myocarditis.
CONCLUSIONS: ECG at the onset of myocarditis manifested as sinus tachycardia and prolonged QTc interval predicted a high risk of severe myocarditis. Early detection of ECG abnormalities may faciliate early detection of severe ICI-associated myocarditis.

Persistent sinus tachycardia (pST) has been associated with adverse cardiovascular events in critically ill patients. Pharmacological control of heart rate with negative inotropic agents has proven to be safe but could be potentially dangerous in patients with concomitant right ventricular (RV) dysfunction. Ivabradine, a medication devoid of negative inotropy, could be a potentially safe solution for this patient population when adequate heart rate control is desired. A 17-year-old male with a history of vaping developed acute respiratory distress syndrome (ARDS) and RV dysfunction, requiring extra corporal life support (ECLS). He suffered from pST. Given his RV dysfunction, a beta-blocker was avoided, and ivabradine was used safely with improvement of his pST. This case demonstrates the efficacy of ivabradine to reduce heart rate and avoid the use of beta-blockers for patients with RV dysfunction, which could be detrimental. Ivabradine was shown to lower the heart rate without altering hemodynamic parameters.

Background Within the cardiovascular system, sinus tachycardia has been a noted finding in patients with post-COVID-19 syndrome (symptoms persisting beyond 12 weeks post-infection). To better understand post-COVID-19 tachycardia, we examined the prevalence of sinus tachycardia 12-16 weeks after diagnosis of SARS-COV-2 infection and its correlation with intensive care utilization, ventilator use, and mortality in vaccinated and unvaccinated patients. Methods We identified adult patients in the TriNetX COVID-19 Research Network with confirmed SARS-COV-2 diagnosis from January 20th, 2020, to February 14th, 2022, and sinus tachycardia 12-16 weeks after diagnosis. Two cohorts were created: patients who developed tachycardia 12 weeks after initial diagnosis and patients without tachycardia. The tachycardia cohort was divided further based on vaccination status. Results Of 1,363,907 patients included, 30,705 (2.2%) developed tachycardia. The patients with tachycardia had more comorbidities. Using propensity score matching (PSM), two cohorts of 30,702 were created. The SARS-COV-2 tachycardic cohort had higher mortality (5.1% vs 2.1%, p<0.001), critical care utilization (5.8% vs 2.2%, p<0.001), and ventilator use (1.8% vs 0.5%, p<0.001). Out of 22,878 patients with persistent tachycardia and recorded vaccination status, 14,840 (65%) were not vaccinated. Mortality (5.9% vs 2.3%, p<0.001), critical care utilization (8.3% vs 3.6%, p<0.001), and ventilator use (3.8% vs 0.6%, p<0.001) were higher in the non-vaccinated patients compared with the vaccinated patients after PSM.  Conclusion The prevalence of persistent tachycardia after SARS-COV-2 infection is notable at 2.2%. Patients with persistent tachycardia have higher mortality rates and demonstrate greater healthcare utilization at one year compared to patients without persistent tachycardia, particularly if unvaccinated.

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BACKGROUND: Supraventricular tachycardias (SVTs), despite having various anatomical substrates and pathophysiological mechanisms, frequently show similar electrocardiographic presentations.
OBJECTIVE: To locate and characterize atrial deflections (ADs) on 12-lead electrocardiograms in dogs with sustained rapid SVT and assess the utility of different electrocardiographic variables in differentiating types of tachycardia.
METHODS: Ninety-two dogs with orthodromic atrioventricular reciprocating tachycardia, 17 with atrial flutter, 33 with focal atrial tachycardia recorded and confirmed by electrophysiological study, and 40 dogs with sinus tachycardia.
METHODS: Atrial deflection position on the 12-lead surface electrocardiogram was assessed according to the sequence of intracardiac activation. Its features were evaluated together with the relationship between AD and QRS complex interval (AD-R) and QRS complex and AD interval (R-AD).
RESULTS: Orthodromic atrioventricular reciprocating tachycardia was characterized by an AD-AD interval of 213 ± 30 ms, mean electrical axis (MEA) of AD of -90 (-90/-78)°, R-AD interval of 75 (65-80) ms, and R-AD/AD-R of 0.54 (0.45-0.64). Atrial flutter was characterized by an AD-AD interval of 199 ± 57 ms, MEA of 76° (72/81), R-AD of 120 (72-144) ms, and R-AD/AD-R of 0.81 (0.63-1.13). Focal atrial tachycardia was characterized by an AD-AD interval of 270 ± 38 ms, MEA of 49 (-72/76)°, R-AD of 160 (120-200) ms, and R-AD/AD-R of 1.45 (0.92-1.67). Sinus tachycardia was characterized by an AD-AD interval of 292 ± 31 ms, MEA of 66° (52/73), R-AD of 215 (192-222) ms, and R-AD/AD-R of 2.68 (2.25-3.08).
CONCLUSIONS: Analyzing AD on 12-lead electrocardiogram is helpful in differentiating the most common SVTs in dogs.

Postural orthostatic tachycardia is a syndrome characterized by an elevated heart rate in response to standing. This syndrome typically presents in late adolescence and early adulthood, with a higher percentage occurring in females. This syndrome is often seen following a viral infection, pregnancy, surgery, or intense psychological stress. This condition presents a wide range of symptoms that vary depending on its unclear etiology. We present the case of a 21-year-old woman with convulsions associated with postural orthostatic tachycardia syndrome after being misdiagnosed with a psychiatric condition for many years.

Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder caused by dystrophin gene mutation resulting in muscle weakness, motor delays, difficulty in standing, and inability to walk by 12 years. As disease progresses, it leads to cardiac and respiratory failure. Evaluation of cardiac autonomic status and echocardiography in DMD patients at a young age can be a potential biomarker to assess disease progression. This study aimed to investigate the younger DMD population of 5-11years of age with mild to moderate cardiac involvement for early detection using non-invasive and cost-effective tools. Genetically confirmed male DMD patients, aged 5-11 years (n = 47), screened from the outpatient department of a tertiary neuroscience institution were subjected to heart rate variability and echocardiographic analysis, and values were correlated with their clinical variables. DMD patients showed a significantly higher difference in HR, interventricular septum, E m/s, and E-wave to A-wave (E/A) ratio than normal values (p < 0.001). Significantly higher HR indicates initial sinus tachycardia and decreased IVD (d), and increased E m/s and E/A ratio mark the onset of cardiac symptoms in DMD patients even though its chamber dimension remains normal and are associated with cardiac muscle fibrosis.

Neuroleptic malignant syndrome (NMS) is a rare, life-threatening emergency caused more commonly by typical antipsychotics. However, unusual presentations of NMS are intermittently reported with the use of atypical antipsychotics. We present the case of a 42-year-old gentleman with schizoaffective and bipolar disorder who was admitted for change in mentation and lithium toxicity. His mentation did not improve despite being dialyzed and the resolution of lithium level to baseline. He developed persistent tachycardia and hyperthermia, initially attributed to Streptococcal infection. But despite appropriate antibiotic therapy, his clinical symptoms did not improve. An extensive workup for his neurological symptoms, including lumbar puncture, 5-hydroxy indole acetic acid urine test, and brain magnetic resonance imaging, was inconclusive of any underlying etiology. Given the suspicion of atypical NMS, bromocriptine 2.5 mg three times daily was initiated. This led to the gradual resolution of his symptoms and a return to his baseline mental status. Diagnosing atypical NMS can be challenging and must be differentiated from similar disorders. Lithium toxicity can predispose patients to develop NMS.

Pre-workout supplement use has increased in recent years. Multiple side effects and off-labeled substances have been reported. We report a case of a 35-year-old patient who recently started a pre-workout and was found to have sinus tachycardia, elevated troponin, and subclinical hyperthyroidism. The echocardiogram showed normal ejection fraction and no wall motion abnormality. Beta-blockade therapy with propranolol was offered, but she refused, and her symptoms and troponin levels improved after proper hydration within 36 hours. A cautious and accurate assessment of young, fitness-enthusiastic patients experiencing unusual chest pain is essential to identify a reversible cardiac injury and possible off-label substances in over-the-counter supplements.

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