BACKGROUND The Apple Watch Series 4 (AW) can detect atrial fibrillation and perform a single-lead electrocardiogram (ECG), but the clinical accuracy of AW ECG waveforms compared to lead 1 of a 12-lead ECG is unclear. OBJECTIVE The purpose of this study was to assess the accuracy of interval measurements on AW ECG tracings in comparison to lead 1 on a 12-lead ECG. METHODS We obtained ECGs at a university hospital of healthy volunteers age .18 years. ECG waveforms were measured with calipers to the nearest 0.25 mm. When possible, 3 consecutive waveforms in lead 1 were measured. Waveform properties, including intervals, were recorded. Concordance correlation coefficients and Bland-Altman plots were used to assess level of agreement between devices. RESULTS Twelve-lead (n 5 113) and AW (n 5 129) ECG waveforms from 43 volunteers (mean age 31 years; 65% female) were analyzed. Sinus rhythm interpretation between devices was 100% concordant. No arrhythmias were recorded. Mean difference (d) for heart rate was 1.16 6 4.33 bpm (r 5 0.94); 3.83 6 113.54 ms for RR interval (r 5 0.79); 5.43 6 17 ms for PR interval (r 5 0.83);-6.89 6 14.81 ms for QRS interval (r 5 0.65);-11.27 6 22.9 ms for QT interval (r 5 0.79); and-11.67 6 27 ms for QTc interval (r 5 0.57). There was moderate (d ,40 ms) to strong (d ,20 ms or , 5 bpm) agreement between devices represented by Bland-Altman plots. CONCLUSION The AW produces accurate ECGs in healthy adults with moderate to strong agreement of basic ECG intervals.

No abstract

Thyrotoxic periodic paralysis is a life-threatening complication of hyperthyroidism characterized by transient episodes of muscle paralysis and hypokalemia, commonly seen in Asian men. We present a rare case of ventricular fibrillation as the initial presentation of thyrotoxic periodic paralysis. ( Level of Difficulty: Intermediate. )

No abstract

is an atypical antipsychotic that affects the dopaminergic pathway and is commonly used in the treatment of schizophrenia and bipolar disorder. Common side effects include extrapyramidal syndrome, akathisia, hyperprolactinemia, weight gain, and transaminitis. Rare adverse effects include hypothermia, bradycardia, and hemodynamic instability, while neutropenia is even more rare. CASE PRESENTATION: A 64-year-old woman with history of schizophrenia was brought in from jail for bilateral lower extremity edema and hypothermia unrelated to environmental exposure. On arrival, she was agitated, hypotensive (MAP <60), bradycardic (HR in 50s), and hypothermic with a rectal temperature of 90.4 F. Due to the patient's psychotic state, no history could be elicited. Initial differential diagnoses included myxedema coma and sepsis. Fluid bolus, antibiotics, intravenous levothyroxine and hydrocortisone were immediately administered. Laboratory findings were significant for neutropenia with an absolute neutrophil count of 984, which was previously normal three weeks earlier. Peripheral smear demonstrated few large granular lymphocytes, which are normal variants. Thyroid studies showed a normal free T4 and mildly elevated TSH with a value of 6.45 mcIU/mL (0.34-5.60 mcIU/ml), consistent with subclinical hypothyroidism. Additional findings included a normal lactate, clear urinalysis, unremarkable chest x-ray, and pan-CT non-revealing for an infectious source. Patient did have bilateral lower extremity erythema and edema concerning for bilateral lower extremity cellulitis, but this was not significant enough to account for her severe hypothermia, bradycardia, and hemodynamic instability. On further investigation, the only medication the patient was taking at the time of presentation was olanzapine, a court-ordered medication for her psychotic symptoms, which was started thirteen days prior to symptoms. During her hospital stay, olanzapine was stopped and switched to aripiprazole (Abilify), which was tolerated well by the patient in the past. Additionally, with active warming and supportive care with fluids and antibiotics, the patient's clinical condition improved. Neutropenia resolved five days after olanzapine was discontinued, and all culture data returned without any sign of infection. DISCUSSION: This case illustrates how rare adverse reactions from an antipsychotic medication can confound the clinical picture and mimic another diagnosis, specifically myxedema coma and sepsis. There have been less than a hundred reported cases of antipsychotic-related hypothermia and only two reported cases of olanzapine-related neutropenia in the literature. CONCLUSIONS: Awareness of these rare adverse reactions, alongside a thorough investigation and open-minded differential were critical in deciphering this intriguing case.