A short RP tachycardia in congenitally corrected transposition. What is the mechanism?

A 51-year-old female with congenitally corrected transposition of great arteries (CCTGA), situs solitus, dextrocardia, atrial septal defect and persistent left superior vena cava underwent electrophysiology study for recurrent palpitations with documented narrow complex, short RP tachycardia. With a catheter in the region of the anterior mitral annulus, a His signal was recorded and HV interval was 35 msec. Tachycardia was induced with a ventricular extrastimulus. During the tachycardia there was 1:1 ventriculo-atrial conduction and central atrial activation with a VA interval of 20 msec. The recorded His signal could be seen after the QRS. What is the mechanism of the tachycardia?

An unusual ECG lead reversal.

Lead reversals are a common cause of electrocardiographic abnormality, which can lead to a false diagnosis like chamber enlargement, myocardial ischemia or infarction. Isolated limb lead reversals and chest lead reversals are common in clinical practice. This article reports a rare case where multiple limb and chest leads were reversed due to the reversal of cables leading to a false diagnosis of myocardial ischemia.

Coumel's sign reversed: What is the mechanism?

A patient presented with documented narrow QRS tachycardia. During electrophysiological study, he has orthodromic reciprocating tachycardia with atrial activation consistent with left free wall accessory pathway. With induction of tachycardia, beats with LBBB morphology have shorter cycle length than those with narrow QRS. What is the mechanism?

Sudden death and its predictors in myocardial infarction survivors in an Indian population.

OBJECTIVE: This study was conducted to assess the incidence of sudden cardiac death (SCD) in post myocardial infarction patients and to determine the predictive value of various risk markers in identifying cardiac mortality and SCD. METHODS: Left ventricular function, arrhythmias on Holter and microvolt T wave alternans (MTWA) were assessed in patients with prior myocardial infarction and ejection fraction ≤ 40%. The primary outcome was a composite of cardiac death and resuscitated cardiac arrest during follow up. Secondary outcomes included total mortality and SCD. RESULTS: Fifty-eight patients were included in the study. Eight patients (15.5%) died during a mean follow-up of 22.3 ± 6.6 months. Seven of them (12.1%) had SCD. Among the various risk markers studied, left ventricular ejection fraction (LVEF) ≤ 30% (Hazard ratio 5.6, 95% CI 1.39 to 23) and non-sustained ventricular tachycardia (NSVT) in holter (5.7, 95% CI 1.14 to 29) were significantly associated with the primary outcome in multivariate analysis. Other measures, including QRS width, heart rate variability, heart rate turbulence and MTWA showed no association. CONCLUSIONS: Among patients with prior myocardial infarction and reduced left ventricular function, the rate of cardiac death was substantial, with most of these being sudden cardiac death. Both LVEF ≤30% and NSVT were associated with cardiac death whereas only LVEF predicted SCD. Other parameters did not appear useful for prediction of events in these patients. These findings have implications for decision making for the use of implantable cardioverter defibrillators for primary prevention in these patients.

Magnetocardiography for identification of coronary ischemia in patients with chest pain and normal resting 12-lead electrocardiogram.

BACKGROUND: Identification of coronary ischemia in patients presenting with chronic chest pain is difficult as resting ECG can be normal. Diagnosis of coronary ischemia requires evaluation during exercise or pharmacological stress. A noninvasive test to identify coronary ischemia at rest without the need for exercise is desirable. We studied the diagnostic accuracy of magnetocardiography (MCG) at rest to detect coronary ischemia in these patients. METHODS: Patients with chronic chest pain and suspected coronary ischemia with a normal ECG were included. Patients underwent treadmill test (TMT) and were divided into TMT positive and TMT negative groups. MCG was recorded in a magnetically shielded room. Iso-field contour maps generated at the T-wave peak were compared between the groups. From the magnetic field map (MFM), the magnetic field angle at T-wave peak was calculated and was also compared across the two groups. RESULTS: There were a total of 29 patients, 12 with positive TMT and 17 with negative TMT. An abnormal magnetic field angle was more common in the TMT positive group (72% vs. 6%). Abnormal contour maps in the form of nondipole patterns or abnormal orientation were seen in 81.8% (9/11) patients in TMT positive group and 6.8% (1/17) patients in the TMT negative group (p < .001). CONCLUSION: Abnormal magnetic field angle and abnormal magnetic field maps in MCG recorded at rest are able to identify the presence of coronary ischemia in patients with chronic chest pain and a normal resting ECG.

Atrial fibrillation and preexcitation - A licence to kill.

Atrial fibrillation becomes a potentially lethal arrhythmia in the presence of preexcitation because the rapid ventricular activation can result in ventricular fibrillation. Fortunately, radiofrequency ablation is an effective treatment for these patients. Specific points of interest regarding this association are the mechanism of increased incidence of atrial fibrillation and the current management of patients presenting in atrial fibrillation. These are discussed in this editorial.

Effects of conscious sedation on tachycardia inducibility and patient comfort during ablation of supraventricular tachycardia: a double blind randomized controlled study.

AIMS: Sedation is not consistently used during electrophysiology procedures because of concerns regarding effects on tachycardia inducibility. We designed this study to assess the effect of conscious sedation on tachycardia inducibility and patient comfort during supraventricular tachycardia ablation. METHODS AND RESULTS: Patients with narrow QRS tachycardia and no pre-excitation undergoing an electrophysiology study were randomly assigned to sedation or placebo group. Patients in the sedation group received intermittent doses of midazolam and fentanyl, while those in the placebo group received normal saline as placebo. The physician and the patient were blinded to the allocation. Information was collected on tachycardia inducibility, patient discomfort, and complications. A total of 103 patients were included in the study. Proportion of patients with difficult tachycardia induction (27.4% vs. 32.7%) or with non-inducibility (5.8% vs. 3.8%) were not different between the sedation and placebo groups. Patient discomfort as measured by the Wong-Baker scale was significantly less in the sedation group (1.45 ± 1.08 vs. 2.24 ± 1.2, P < 0.0007) compared to the placebo group. There was no difference in incidence of hypotension or hypoxia between the two groups. CONCLUSIONS: Conscious sedation with intermittent midazolam- and fentanyl-reduced patient discomfort during electrophysiology study and ablation of supraventricular tachycardia without affecting tachycardia inducibility. Sedation administered in the absence of an anaesthetist was safe.

Infra-His Block during Atrial Pacing-Functional or Pathological?

The significance of infra-His conduction abnormalities observed in the electrophysiology lab can be difficult to assess. In this report we show infra-His conduction block during programmed atrial stimulation in a patient and discuss if this should be considered functional or pathological.

Noninvasive Determination of HV Interval Using Magnetocardiography.

BACKGROUND: The His-ventricular (HV) interval is an important index of atrioventricular conduction, but at present can be reliably measured only during an invasive electrophysiology (EP) study. Magnetocardiography (MCG) is a noninvasive measurement of weak magnetic fields generated by the heart. We compared HV interval noninvasively assessed using MCG with the corresponding values measured directly in an EP study. METHODS: MCG was measured using a 37-channel system inside a magnetically shielded room in patients who had previously undergone an EP study. His-bundle potential was identified in the PR segment after signal averaging. Magnetic field maps representing the spatial distribution of ramp-like signals in the PR segment generated at various instants of time were used to identify His-bundle signals in cases where the deflection representing the His was ambiguous. RESULTS: The study included 23 patients (14 male, nine female) with a wide range of HV intervals measured during EP study (49 ± 17 ms, range 35-120 ms). In 21 (91%) subjects, discernible His-bundle signals are observed in the PR segment of MCG traces. HV intervals measured between the two methods showed a correlation (r2 = 0.87, P < 0.0001) with a mean difference of 5.4 ± 3.2 ms. CONCLUSION: With the use of new criteria to identify the His-bundle deflection in signal-averaged MCG signals, we report a high success rate in noninvasive HV interval measurement and a good agreement with those from EP study. The results encourage the use of MCG as a noninvasive method for measurement of the HV interval.

Which side are you on? - Deducing the chamber of origin of atrial tachycardia.

Atrial arrhythmias rising from the regions of the atria that are in close proximity to each other may pose a challenge in identifying the chamber to map and ablate in. In this report, we discuss a patient with left atrial tachycardia which initially mimicked right atrial tachycardia. We discuss the origins of the abnormal electrograms in the right atrium and how this provides a general understanding of the mechanism of double potentials.

Jumping across the gap - a series of atrial extrastimuli.

The "gap phenomenon" is an interesting phenomenon in electrophysiology arising from the differences in refractory periods at two or more levels of the atrioventricular (AV) conduction system. We present a patient with dual AV nodal physiology in whom the AH jump mediates the gap phenomenon. We also briefly discuss the other mechanisms of gap phenomenon that have been described in this setting.