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Background: The micro waveform of His bundle potential can't be recorded beat-to-beat on surface electrocardiogram yet. We have found that the micro-wavelets before QRS complex may be related to atrioventricular conduction system potentials. This study is to explore the possibility of His bundle potential can be noninvasively recorded on surface electrocardiogram.Methods: We randomized 65 patients undergoing radiofrequency catheter ablation of paroxysmal superventricular tachycardia (exclude overt Wolff-Parkinson-White syndrome) to receive "conventional electrocardiogram" and "new electrocardiogram" before the procedure. His bundle electrogram was collected during the procedure. Comparative analysis of PAs (PA interval recorded on surface electrocardiogram), AHs (AH interval recorded on surface electrocardiogram) and HVs (HV interval recorded on surface electrocardiogram) interval recorded on surface "new electrocardiogram" and PA, AH, HV interval recorded on His bundle electrogram was investigated.Results: There was no difference (P > 0.05) between groups in HVs interval (49.63 ± 6.19 ms) and HV interval (49.35 ± 6.49 ms). Results of correlational analysis found that HVS interval was significantly positively associated with HV interval (r = 0.929; P < 0.01).Conclusions: His bundle potentials can be noninvasively recorded on surface electrocardiogram. Noninvasive His bundle potential tracing might represent a new method for locating the site of atrioventricular block and identifying the origin of a wide QRS complex. [ABSTRACT FROM AUTHOR]

The Brugada syndrome is a genetic disease (mutation of the SCN5A gene) that predisposes to syncope and life-threatening sudden cardiac death. The case highlights the importance of recognizing hyperkalemia, as potential triggers of the acquired Brugada sign with electrical alternans. [ABSTRACT FROM AUTHOR]

We reported a case about the slow heart rate and regular heart rhythm that appeared after administration of digitalis, diuretics and potassium in a patient with chronic atrial fibrillation ten years. ECG characteristics demonstrated the special changes about hyperkalemia as follows: f waves disappeared; nonspecific widened QRS complex appeared; RR interval was regular; and heart rate slowed. T wave inversion reverted to be symmetrical and peaked. Laboratory investigations were noteworthy for serum potassium elevations (serum potassium was 8.50 mmol/L). In patients with chronic atrial fibrillation, digitalis administration, diuretic therapy and potassium supplementation can induce slow heart rate and regular heart rhythm. These changes may permit prompt recognition of overt digitalis toxicity-atrioventricular block. However, these have also frequently been seen in the setting of chronic renal insufficiency, resulting in hyperkalemia. The basic principles of treatment were different in these two conditions. Therefore, ECG and laboratory investigation should draw a clinician's attention. [ABSTRACT FROM AUTHOR]