Search

A 42-year old female with no significant past medical history, normal physical exam, and normal routine lab studies presents with “thumps” in her chest. A Holter monitor evaluation revealed normal sinus rhythm with two different PR intervals suggesting “dual AV nodal pathways” and occasional blocked P waves with junctional escape complexes. The behavior was most suggestive that no conduction through either pathway reached the His bundle, suggesting distal block must be beyond each pathway, but still within the AV node. These strips are shown. Their interpretation is discussed, along with the underlying explanation and significance.

Differences in successive R-R intervals (RRIs) were normalized by RRIs before and after the indexing beats (normalized DRs) in individuals with normal sinus rhythm (NSR) and 98.89% of normalized DRs were found to distribute within mean ± 0.100 (≒mean ± 3SD), whereas 73.47% were out of this range in atrial fibrillation (AF). When 7 out 20 normalized DRs fell outside of 0.000 ± 0.100, NSR (n = 129) and AF (n = 108) could be discriminated with high sensitivity, specificity, and predictive values (>99.0% for all). This method will be used in detecting AF candidates from a small number of heart beats or arterial pulses.

Junctional ectopic tachycardia(JET) is a rare childhood arrhythmia originating from the area adjacent to the atrioventricular(AV) node. It often occurs after surgical procedures like repair of Tetralogy of Fallot, atrioventricular septal defect and ventricular septal defect, which are all performed in that area. While AV block (AVB) can occur after JET, it is very rare for late JET occurring after early postoperative AVB to be followed by normal sinus rhythm (NSR). There is no information in the literature related to the pathophysiology of this phenomenon. In this text, we present 4 patients who developed complete AV block(CAVB) in the early postoperative period (within the first 24h) after JET in late period (>72h) and returned to NSR with first-degree AV block and then NSR during follow-up. Based on these cases, we hypothesize that there is a link between late JET after early postoperative CAVB and return to NSR.

The relationship between the degree of electrical organization of ventricular fibrillation (VF) and defibrillation success was investigated in this study using a new technique to quantify organization—spatial coherence. This technique employs the use of the magnitude-squared coherence spectrum to analyze multichannel electrograms obtained during a cardiac mapping study. Magnitude-squared coherence values for all possible pairs of electrograms recorded from an epicardial plaque consisting of 112 electrodes were computed. Average coherence was plotted versus electrode separation distance, and the data were fit with an exponentially decaying curve. Two parameters indicative of myocardial organization were extracted from the curve. The coherence length (d) was defined as the distance (mm) at which the average coherence dropped to a given level, and the coherence strength was defined as the average coherence value at a given distance. Higher values for these parameters were hypothesized to indicate higher levels of organization. The spatial coherence technique was tested previously in a canine study of ventricular fibrillation (VF) and normal sinus rhythm, and the results suggested that spatial coherence parameters may be used to compare cardiac rhythms in terms of their organization. To test the hypothesis that organization is related to defibrillation success, 164 mapping sessions recorded during repeated VF induction and defibrillation trials using a monophasic waveform were performed in a close-chested canine study (n = 9) using a fixed energy and VF duration (10 seconds). Three coherence lengths and five coherence strengths were calculated for each VF episode. Results using a two-way analysis of variance with blocking between dogs showed that all of the coherence length and three of the coherence strength parameters were higher for those VF episodes that were successfully defibrillated than for those that were not (P < .05). Energy delivered and transmyocardial impedance were not significantly different between the groups. The authors conclude (1) the organization of a VF episode, as reflected in the spatial coherence parameters, is related to defibrillation success and may be partially responsible for the probabilistic nature of defibrillation and (2) the spatial coherence technique provides a means of quantifying myocardial electrical organization and is an important experimental tool that may be used to obtain a better understanding of VF and its termination.

An electrocardiogram marker to detect patients who have paroxysmal atrial fibrillation (PAF) is reported. The data set of ECG records made available by PhysioNet for Cardiology Challenge 2001 was used. The method uses a filtered time series with a frequency range between 3 and 9 Hz obtained from the electrocardiogram record. Typically, frequencies observed when a patient is in atrial fibrillation and atrial flutter is within this frequency range. Filtering was done using wavelets. Thereafter, the temporal properties of this filtered time series are studied. The temporal properties studied are the standard deviation, standard deviation of successive differences, and the length of the ellipse in the Poincare plot. The results indicate that these temporal properties of patients with PAF are depressed compared to the healthy group. A marker based on these temporal properties shows promise in detecting PAF when patients are in normal sinus rhythm. Results also show that the values for these temporal properties for a patient with PAF show little variation with time, and its measure is not dependent on the time of occurrence of a PAF episode.

Objective We analyzed the accuracy with which a computer algorithm reads electrocardiograms (ECGs) with electronic pacemakers (PMs). Methods Electrocardiograms were screened for the presence of electronic pacing spikes. Computer-derived interpretations were compared with cardiologists' readings. Results Computer-drawn interpretations required revision by cardiologists in 61.3% of cases. In 18.4% of cases, the ECG reading algorithm failed to recognize the presence of a PM. The misinterpretation of paced beats as intrinsic beats led to multiple secondary errors, including myocardial infarctions in varying localization. The most common error in computer reading was the failure to identify an underlying rhythm. This error caused frequent misidentification of the PM type, especially when the presence of normal sinus rhythm was not recognized in a tracing with a DDD PM tracking the atrial activity. Conclusion The increasing number of pacing devices, and the resulting number of ECGs with pacing spikes, mandates the refining of ECG reading algorithms. Improvement is especially needed in the recognition of the underlying rhythm, pacing spikes, and mode of pacing.

Introduction: The 10-100 μV foetal electrocardiogram can be recorded from the maternal abdominal surface from ~12 weeks gestational age (WGA), and RR, PR, QR and QT intervals, and T and P wave dispersions extracted. These non-invasive measures provide quantitative information on sino-atrial node pacemaking rate (via RR), propagation times and velocities (via PR, QT), and ventricular action potential duration and its restitution (QT-RR) during foetal normal sinus rhythm. Arrhythmias are observed in b5% of recordings. Methods: The parameters of biophysically detailed models of adult human cardiac cell electrophysiology, based on voltage clamp, immune-histochemical and mRNA expression data were modified, informed by data from the literature on animal foetal tissue and cardiomyocytes derived from human stem cell lines, to reproduce human foetal RR and QT intervals. One dimensional partial differential equation models of SAN, atrial, AVN and ventricular tissue, with lengths from MRI and intercellular coupling informed by PR and QR intervals, were constructed for hearts from 15–40 WGA. Numerical solutions, with zero-flux boundary conditions, were by the explicit Euler method with time and space steps Δt = 0.005 ms and Δx = 0.1 mm. Results: The 1D model at 15, 30 WGA gave NSR intervals RR: 400, 450; QR: 200, 280 ms. Spatially uniform progressive reduction of {gCa,L and gCa, T} slowed the SAN, and led to AV conduction blocks. Self terminating and persistent re-entry with a period of 340–350 ms within a 1-D ring ventricular tissue model. Conclusion: The preliminary 1-D family of models reproduces the observed timings of fECG intervals from 15–40 WGA, the characteristics of development of foetal AV block, and self terminating ventricular tachycardia.

His bundle electrograms were recorded in 42 patients with secundum atrial septal defects (ASD) and in 50 controls, aged 1 month to 16 years, in normal sinus rhythm and with normal PR intervals. Intervals PA (P less than 0.01) and PR (P less than 0.02) were found to be significantly prolonged in ASD patients. Analyzing the results according to age, a significant increase for intervals AH (P less than 0.05), HV (P less than 0.001) and PR (P less than 0.001) was noted in the oldest ASD children as compared to the younger ASD children, whereas in controls only the PR interval was found to be significantly prolonged (P less than 0.05) in the oldest subgroup. Under the age of three years, atrioventricular conduction intervals were not significantly different whether or not an ASD was present. However, in older children with ASD as compared to controls, a significant increase was noted for interval PA (P less than 0.03) in children four to eight years old and for intervals HV (P less than 0.01) and PR (P less than 0.001) in children 9 to 16 years old. ASD patients showed a more significant correlation with age for interval PR with a significantly steeper slope of the regression line. Results show the impact of ASD on AV conduction to be age-related, with involvement not only of the PA interval but also of the HV interval.

A criterion to determine the indication for pacemaker implantation in the sick sinus syndrome by overdrive suppression is proposed. Overdrive suppression was performed in 10 patients with the sick sinus syndrome (SSS) and another 10 patients with normal sinus rhythm (NSR) who served as controls. In the SSS group, 9 patients had complained of such severe symptoms as Adams-Stokes attack and/or congestive failure and were referred to our laboratory for pacemaker implantation. One other patient, an apparently robust young man (20 years old) referred for detailed cardiac examination, had no remarkable symptoms except for arrhythmias, but was found dead two months later. Atrial pacing for overdrive suppression was carried out at first at various rates ranging from 60 to 180 beats/min for 15 sec, and then at a rate of 100 beats/min for various durations ranging from 5 to 180 sec. After cessation of the atrial pacing, asystolic pauses were measured and the maximum (maximum pause) among the pauses obtained was used as a parameter indicating depression of cardiac automaticity. The maximum pause in the SSS group ranged from 5.6 to 9.0 sec (mean +/- SD = 7.0 +/- 1.2), WHILE THOSE IN THE NSR group ranged from 0.7 to 1.5 sec (mean +/- SD = 1.2 +/- 0.14). Therefore, the maximum pause was considered not only to reflect the severity of the symptoms necessitating pacemaker implantation in the 9 patients of the SSS group but to have warned us of sudder death in another patient. We concluded that overdrive suppression is useful as a supplementary challenge to determine indications for pacemaker implantation for the sick sinus syndrome, and that prolongation of the maximum pause beyond 5.0 sec is the critical level for pacemaker implantation.

Summary Atrial dissociation is a very rare, transient arrhythmia frequently associated with intractable congestive heart failure. A case of atrial dissociation in a 48-year-old woman was observed in the first 72 hours of her recent inferolateral and probably atrial infarction. The slow unilateral rhythm was registered in the presence of sinus rhythm, 2:1 AV block, advanced AV block and ventricular pacemaker stimulation, respectively. The simultaneous right atrial electrogram indicated the origin of the isolated slow rhythm as left atrial. After temporary pacemaker therapy the atrial dissociation disappeared within three days; on the fifth day the normal sinus rhythm was restored spontaneously.

Summary We describe a patient in whom procainamide induced the appearance of late potentials during intraoperative sinus rhythm electrogram mapping. Only nonsustained ventricular tachycardia (VT) could be induced while off all antiarrhythmic drugs. After administration of the procainamide, programmed stimulation induced sustained VT coincident with the appearance of late potentials during sinus rhythm. The late potential was recorded from the same site, during normal sinus rhythm, where mid to late diastolic activation during VT was recorded, and where cryotermination occurred during cryomapping. We hypothesize that procainamide slowed conduction, manifested as prolongation or appearance of late potentials in sinus rhythm, and facilitated induction of sustained reentrant ventricular tachycardia.

Summary A case of Prinzmetal's variant angina pectoris was discovered mainly by the use of dynamic electrocardiography (DECG). This diagnosis prompted this patient's admission to the hospital where ventricular fibrillation was successfully converted to normal sinus rhythm. A coronary angiogram revealed a singular isolated stenosis of the left anterior descending coronary artery which was successfully bypassed with a saphenous vein graft. The validity of ST segments recorded by DECG is discussed. This report demonstrates that DECG may be the only way to diagnose variant angina pectoris.

Summary We studied the pattern of endocardial and epicardial activation during normal sinus rhythm and ventricular arrhythmias in 42 mongrel, dogs immediately after coronary artery ligation. The electrocardiogram (ECG) and seven single or composite electrograms were recorded from various endocardial and epicardial sites within and surrounding the ischemic area. Fragmentation and diastolic conduction delay originating in the central ischemic epicardial area preceded the appearance of ventricular arrhythmias during sinus rhythm and normal AV conduction. In all experiments, the activation pattern in the ischemic zone following diastolic epicardial bridging was associated with early spread into the ischemic endocardial zone, and then to all the remaining protions of the heart. We never observed direct epicardial spread to the normal areas of the heart. Likewise, evidence of automatic activity could not be detected during this period of acute ischemia. Isolated premature endocardial activation was frequently noted late in diastole. Progressive earlier endocardial activation in the ischemic zone was associated with the emergence of manifest ventricular arrhythmias. Delayed epicardial activation and fragmentation appeared to engender rapid and irregular endocardial activation, which then appeared to be transmitted to the normal epicardium and to produce ventricular arrhythmias and fibrillation. The ischemic endocardial area may play an important role in the genesis of the dangerous reentrant ventricular arrhythmias associated with acute ischemia.

Summary Presented is a case of distal renal tubular acidosis, with secondary hypokalemia and 2:1 A-V block that reverted to normal sinus rhythm with oral potassium supplements. The rhythm reverted to atrial flutter with second degree A-V block upon discontinuation of the additional K + . This continued until potassium supplements were again administered.