Regular narrow QRS tachycardia. What is the mechanism?

A 45-years-old lady with no structural heart disease on echocardiogram presented with recurrent episodes of palpitation. There was no baseline preexcitation. Twelve lead surface electrocardiograms (ECG) recorded during one of the episodes are provided. What is the likely mechanism of the tachycardia? [Figure: see text].

Etiology and Outcomes of Syncope in Patients With Structural Heart Disease and Negative Electrophysiology Study.

OBJECTIVES: This study sought to determine the cause of recurrent syncope and clinical outcomes by using the head-up tilt test (HUTT) and an insertable loop recorder (ILR) in patients with structural heart disease (SHD) and negative electrophysiology study (EPS) results. BACKGROUND: Patients with syncope and SHD with negative EPS findings have a low risk of sudden cardiac arrest. Nevertheless, the cause of recurrent syncope and the outcomes in these patients are not well characterized. METHODS: This prospective study evaluated syncope patients with SHD and negative EPS results by using HUTT (with sublingual nitroglycerine [NTG] provocation as needed) and ILR. A total of 41 SHD patients (27 patients [66%] had coronary arterial disease, and 14 patients [34.15%] had dilated cardiomyopathy with mean EF of 42 ± 4.8% [range 30% to 49%]) were included. RESULTS: HUTT findings were positive in 25 patients (61%) in group A and negative in 16 patients (39%) in group B. An ILR was implanted in 21 of 25 group A patients (84%) and in 12 of 16 group B patients (75%), and they were followed for 15 ± 8 months. During follow-up, 17 of 21 patients (81%) in group A and 5 of 12 patients (41.7%) in group B had ILR evidence consistent with reflex syncope. One group B patient had documented atrioventricular block and underwent pacemaker implantation. There were no malignant ventricular arrhythmias or deaths on follow-up. CONCLUSIONS: Reflex syncope is the most common cause of syncope and accounts for approximately 60% of cases in patients with SHD, negative EPS results, left ventricular systolic dysfunction with left ventricular EF >30%, and not in heart failure.

Supra-Hisian Conduction Block as an Unusual Presenting Feature of Takotsubo Cardiomyopathy.

BACKGROUND: Atrioventricular (AV) block is rare in Takotsubo cardiomyopathy (TC). CASE REPORT: A 66-year-old female presented with fatigue. Her electrocardiogram revealed 3:2 Mobitz Type II AV block, confirmed to be supra-Hisian by electrophysiological study. Echocardiogram and left ventricular angiogram showed moderate left ventricular dysfunction and apical ballooning, whereas coronary angiogram revealed mildly ectatic coronaries. At 2 weeks AV block persisted, needing permanent pacemaker implantation. At 1-month follow-up, she had normal ventricular function and no AV block. CONCLUSION: Delayed recovery of AV conduction is possible in TC, thus implying to wait for a longer period before implanting a pacemaker.

Comparison of Efficacy, Pattern of Response, Occurrence of Arrhythmias, and the Tolerability of Nitroglycerine and Isoprenaline as Provocative Drugs During Head-Up Tilt Test.

BACKGROUND: Various protocols exist for performing head-up tilt test (HUTT). Serious ventricular arrhythmias have been reported during HUTT using Isoprenaline (ISO) provocation and their incidence with sublingual Nitroglycerine provocation is unknown. This study aims to assess the efficacy, pattern of response, tolerability, and frequency of arrhythmias during head-up tilt test with sublingual Nitroglycerine (NTG) provocation compared to ISO) provocation. METHODS: This is a retrospective observational study. RESULT: From 2007 to 2015, a total of 816 patients (68% men, median age 49 IQR 25.75-65 years) underwent head-up tilt testing using sublingual NTG provocation whereas ISO was used in 189 patients (66.1% men, median age 48 IQR 36-60 years). A positive response was more frequently observed in the NTG group than the ISO group (48.4% vs 35.9%, p=0.002), with more frequent type II b (cardio-inhibition with >3sec asystole) and type III (vasodepressor) responses ([15. 9% vs 4.1%, p=0.001] and 0% vs 29.4%, p=0.004) respectively. Bradyarrhythmias occurring always as a part of a positive HUTT response were the commonest arrhythmias (29% in NTG group vs 25.4% in ISO group, p=0.31). Tachyarrhythmias (or premature beats) were more frequent in the ISO group (12.7% vs 7.9%, p=<0.005). The use of NTG was significantly associated with a positive response (OR 1.775, 95% CI 1.269-2.483, p=0.001), whereas the use of ISO predicted the occurrence of premature beats/tachyarrhythmias (OR 3.06, 95% CI 2.195-4.267, p<0.005). Intolerance needing termination of the test was significantly more frequent in the ISO group than NTG group (1.6% vs 0.12%, p= 0.02). CONCLUSION: Head-up tilt test with NTG provocation has a higher yield of a positive response, lower incidence of unwanted arrhythmias and better tolerability compared to ISO. The occurrence of VASIS type II b and type III response was more with Nitroglycerine than Isoprenaline.