Electro-vectorcardiographic analysis of the negative, diphasic and bifid T wave in right precordial leads in young subjects

Morphology, genesis and incidence of isolated T wave abnormalities on right precordial leads of healthy young individuals were studied in this work. ECG were obtained from 1510 healthy subjects aged 14 to 40 years consecutively submitted to a cardiological evaluation in order to assess their fitness for sport. In 510 of them a VCG was made too. The results showed that T waves were rarely negative beyond V1 (0.46%) and even more rarely negative from V1 to V3 (0.13%); diphasic T waves were present in 2.38% and bifid T waves in 6.15% of our cases. The T loop of VCG tended to be more posteriorly displaced and evolved from a counterclockwise to a clockwise rotation as the presence of negative T waves spread toward left on precordial leads. The "+-" type of diphasic T wave corresponded to a counterclockwise rotation of the T loop, the "-+" type to a clockwise rotation. Bifid T waves were associated with figure of eight or "arched" T loops of VCG. The T loops of those subjects who underwent a second evaluation after several years tended to be displaced more anteriorly, with counterclockwise rotation. The causes of these T wave abnormalities have not been clearly explained yet, even if a slight delay in the right final vectors was present in the majority of our cases.     

Electrocardiographic Patterns and Results of Radiofrequency Catheter Ablation of Clockwise Type I Atrial Flutter

Clockwise Rotation of Atrial Flutter. Introduction: Counterclockwise right atrial propagation is usually observed in common atrial flutter, but little is known regarding flutter with clockwise right atrial rotation. The aim of this study is to describe the ECG characteristics and results of catheter ablation of atrial flutter with clockwise right atrial rotation.
Methods and Results: Among the 38 patients with type I atrial flutter in this study population, right atrial impulse propagation was counterclockwise in 20 and clockwise in 8. In the remaining 10 patients, both clockwise and counterclockwise patterns were seen. Clinical and ECG parameters associated with clockwise flutter were compared to those of 28 cases of counterclockwise atrial flutter. Ablation was performed in 11 of 18 cases using a technique identical to that used for counterclockwise flutter. A classical "sawtooth" pattern of the flutter wave was observed in 28 of 28 counterclockwise and 14 of 18 clockwise flutter. A shorter plateau phase, a widening of the negative component of the F wave in the inferior leads, and a negative F wave in V₁ were the most consistent findings in clockwise flutter. Coronary sinus recording always showed septal to lateral left atrial impulse propagation. Ablation was successful in 11 of 11 cases of clockwise flutter in whom this procedure was performed, with 9.5 ± 11.6 radiofrequency pulses delivered between the tricuspid valve and the coronary sinus ostium (n = 5) or the inferior vena cava (n = 5), and in the proximal coronary sinus (n = 1). After a follow-up of 46.6 weeks, two recurrences of clockwise flutter were encountered, which were successfully treated with a second session.
Conclusion: Contrary to commonly accepted concepts, clockwise rotation of atrial flutter Ls not an infrequent phenomenon and can mimic counterclockwise rotation. It can also be successfully ablated by radiofrequency pulses.     

New electrocardiographic criteria for the differentiation between counterclockwise and clockwise atrial flutter: correlation with electrophysiological study and radiofrequency catheter ablation

Objective—To develop new electrocardiographic (ECG) criteria for the differentiation between counterclockwise and clockwise atrial flutters.
Background—Traditionally, the ECG differentiation between counterclockwise and clockwise atrial flutters is based on the flutter wave polarity in the inferior leads. However, determination of flutter wave polarity is subjective and sometimes difficult, especially in flutter waves of undulating pattern.
Patients—The study comprised 37 consecutive patients with drug resistant atrial flutter; 30 had counterclockwise and 17 had clockwise atrial flutter (10 had both forms of atrial flutter). The isthmus dependence was confirmed by entrainment study and catheter ablation. The ECG patterns of both types of atrial flutter were compared and the flutter wave polarity in the inferior leads was determined by four independent cardiologists.
Results—The flutter wave polarity in the inferior leads appeared negative in 24, positive in one, and equivocal in five of the counterclockwise atrial flutters; polarity appeared negative in one, positive in 10, and equivocal in six of the clockwise atrial flutters. However, the aVF/lead I flutter wave amplitude ratio was > 2.5 in all counterclockwise but < 2.5 in all clockwise atrial flutters. The flutter wave nadirs in the inferior leads corresponded to the upstrokes in V1 in all counterclockwise atrial flutters, but corresponded to the downstrokes in V1 in all clockwise atrial flutters.
Conclusions—The flutter wave polarity in the inferior leads does not correlate well with the flutter wave rotating direction. However, counterclockwise and clockwise atrial flutters can be differentiated by new ECG criteria with high accuracy.

Keywords: atrial flutter;  radiofrequency catheter ablation;  electrocardiography     

Coronary sinus pacing initiates counterclockwise atrial flutter while pacing from the low lateral right atrium initiates clockwise atrial flutter: Analysis of episodes of direct initiation of atrial flutter

Introduction: Rapid atrial pacing in sinus rhythm may directly induce atrial flutter without provoking intervening atrial fibrillation, or initiate atrial flutter indirectly, by a conversion from an episode of transient atrial fibrillation provoked by rapid atrial pacing. The present study was performed to examine whether or not the direct induction of clockwise or counterclockwise atrial flutter was pacing-site (right or left atrium) dependent. Methods and Results: We analyzed the mode of direct induction of atrial flutter by rapid atrial pacing. In 46 patients with a history of atrial flutter, rapid atrial pacing with 3 to 20 stimuli (cycle LENGTH = 500 − 170 ms) was performed in sinus rhythm to induce atrial flutter from 3 atrial sites, including the high right atrium, the low lateral right atrium, and the proximal coronary sinus, while recording multiple intracardiac electrograms of the atria. Direct induction of atrial flutter by rapid atrial pacing was a rare phenomenon and was documented only 22 times in 15 patients: 3, 11, and 8 times during stimulation, respectively, from the high right atrium, low lateral right atrium, and the proximal coronary sinus. Counterclockwise atrial flutter (12 times) was more frequently induced with stimulation from the proximal coronary sinus than from the low lateral right atrium (8 vs 1, P = .0001); clockwise atrial flutter (10 times) was induced exclusively from the low lateral right atrium (P = .0001 for low lateral right atrium vs proximal coronary sinus, P = .011 for low lateral right atrium vs high right atrium). Conclusions: Direct induction of either counterclockwise or clockwise atrial flutter was definitively pacing-site dependent; low lateral right atrial pacing induced clockwise, while proximal coronary sinus pacing induced counterclockwise atrial flutter. Anatomic correlation between the flutter circuit and the atrial pacing site may play an important role in the inducibility of counterclockwise or clockwise atrial flutter.     

Electrophysiologic Characteristics and Radiofrequency Catheter Ablation in Patients with Clockwise Atrial Flutter

RF Catheter Ablation of Clockwise Atrial Flutter. introduction: Although the mechanism and radiofrequency catheter ablation of counterclockwise (typical) atrial flutter have been studied extensively, information about the electrocardiographic and electropbysiologic characteristics and effects of radiofrequency ablation in patients with clockwise atrial flutter is limited. Methods and Results: Thirty consecutive patients with clinically documented paroxysmal clockwise atrial flutter were studied. Endocardial recordings and entrainment study using a “halo” catheter with 10 electrode pairs in the right atrium were performed. Radiofrequency energy was applied to the inferior vena cava-tricuspid annulus (IVC-TA) and/or coronary sinus ostium-tricuspid annulus (CSO-TA) isthmus to evaluate the effects of linear catheter ablation. Eighteen patients had both counterclockwise and clockwise atrial flutters, and 12 patients had only clockwise atrial flutter. Both forms of atrial flutter had similar flutter cycle lengths (232 ± 30 vs 226 ± 25 msec, P = 0.526) but reverse activation sequences. Right atrial pacing at a cycle length 20 msec shorter than the flutter cycle length from the CSO-TA isthmus, IVC-TA isthmus, and the area between the two isthmuses revealed concealed entrainment with stimulus-to-P wave intervals of 32 ± 19, 95 ± 14, and 50 ± 17 msec (P = 0.022) in the counterclockwise form, and 110 ± 12, 40 ± 20, and 60 ± 15 msec (P = 0.018) in the clockwise form. In clockwise atrial flutter, 20 patients with biphasic P waves in the inferior leads had the presumed exit site of slow conduction area located at the low posterolateral right atrium; 10 patients with positive P waves in the inferior leads had the presumed exit site located at the mid-high posterolateral right atrium. Among the 18 patients with both forms of atrial flutter, linear ablation lesions directed at the IVC-TA isthmus eliminated both forms of atrial flutter in 14 patients; in the remaining 4 patients. CSO-TA linear lesions eliminated the counterclockwise form and IVC-TA lesions eliminated the clockwise form. Among the 12 patients with the clockwise form only, CSO-TA linear lesions eliminated flutter in 2 and IVC-TA linear lesions eliminated flutter in 10 patients. Successful ablation was confirmed by creation of bidirectional conduction block in the IVC-TA and/or CSO-TA isthmus during pacing from the proximal coronary sinus and right posterolateral atrium sandwiching the linear lesions. During the follow-up period of 17 ± 8 months, 2 patients had recurrence of clockwise atrial flutter, 1 patient had new onset of atypical atrial flutter, and 2 patients had new onset of atrial fibrillation. Conclusions: Counterclockwise and clockwise atrial flutters may have overlapping slow conduction areas with different exit sites. Radiofrequency catheter ablation using the linear method directed at the IVC-TA and CSO-TA isthmuses was feasible and effective in treating both forms of atrial flutter.     

Vectorcardiograms in severe aortic insufficiency. Clockwise rotation of QRS loop in the horizontal plane.

In La Paz Hospital, Madrid, recently, vectorcardiograms (VCGs) were performed on 74 patients with aortic insufficiency. These cases presenting electrocardiographic and radiologic signs of left ventricular hypertrophy, were divided into three groups. In 25 patients (Group 1) the QRS loop in the horizontal plane (HP) showed counterclockwise rotation; 43 patients (Group 2) showed clockwise rotation; and 6 patients (Group 3) showed a pattern of left bundle branch block (LBBB). In Group 2, 31 of the 43 patients (group 2-A) had a Qloop of normal orientation and generally increased voltage, and in the remaining 12 patients (group 2-B) the Q loop was absent. All of the patients in Group 2 had severe aortic insufficiency. Thus, that group's valuation of the left ventricular hypertrophy using maximum QRS vector voltage in the HP, was higher than in Group 1 mean 3.75mV in Group 2 versus mean 2.71mV in Group 1 (p less than 0.01). Postoperative VCGs were performed in 12 patients of group 2-A, showing in all of them a clockwise to counterclockwise rotation change of the QRS loop in the HP. On the other hand, this fact was observed in only two of the eight patients in group 2-B. The clockwise rotation of the QRS loop in the HP is an important datum in our report, particularly in the diagnosis of severe aortic insufficiency. Conversely, a clockwise to counterclockwise rotation change would be a positive sign of good post operative evolution. Finally, two reasons are given to explain this anomalous rotation in the horizontal plane: dilatation and fibrosis.     

Mechanisms of atypical flutter wave morphology in patients with isthmus-dependent atrial flutter

Sixty-three episodes of isthmus-dependent atrial flutter (AFL) in 55 patients were studied to characterize variations in flutter wave morphology and to investigate the mechanisms of the atypical flutter waves on surface ECG. The activation patterns of coronary sinus (CS) and their relationship with flutter wave morphology on the ECG were analyzed. In 46 episodes of counterclockwise AFL (CCW-AFL), there were four types of flutter waves on ECG. Typical and atypical flutter waves were found in 47.8% and 13.0% of the episodes, respectively. Atypical flutter waves had broad positive terminal portion or entirely positive wave in the inferior leads and in V₁, with a distal-to-proximal or fused activation pattern in the CS, and an average activation time of 21.3 ± 11.4 ms. In 17 episodes of clockwise AFL (CW-AFL), typical and atypical flutter waves were identified in 41.2% and 41.2%, respectively. Atypical flutter waves had negative waves in the inferior ECG leads and in V1, a proximal-to-distal activation pattern in the CS, and an average activation time of 42.4 ± 14.4 ms. We conclude that atypical flutter waves are common in the isthmus-dependent AFL. The clockwise or counterclockwise conduction in the right atrium, and the activation patterns or conduction sequences between the right and the left atrium, are associated with the variations in the flutter wave morphology on body surface ECG.     

Atrial Macroreentry Involving the Myocardium of the Coronary Sinus: A Unique Mechanism for Atypical Flutter

Macroreentry Involving the Coronary Sinus. Atrial flutter involving either clockwise or counterclockwise rotation around the tricuspid annulus utilizing the subeustachian isthmus has been well described. However, macroreentrant atrial circuits in atypical atrial flutter in patients who have not undergone previous surgery or without atrial disease are not well defined. We describe a patient without structural heart disease who presented with an atrial macroreentrant rhythm. Entrainment mapping demonstrated a critical isthmus within the coronary sinus. Activation mapping demonstrated double potential throughout the length of the coronary sinus with disparate activation sequences. A circuit involving the myocardium of the coronary sinus, exiting in the lateral left atrium, down the interatrial septum, and reentering into the coronary sinus was identified. Successful ablation of the rhythm was accomplished by a circumferential radiofrequency application within the coronary sinus.     

Pseudo Sinus Rhythm Originating from the Left Superior Pulmonary Vein in a Patient with Paroxysmal Atrial Fibrillation

We report the case of a patient with paroxysmal atrial fibrillation in whom the background cardiac rhythm falsely mimicked sinus rhythm but actually originated from the left superior pulmonary vein. P waves during the ectopic rhythm were flat in lead I, negative in lead aVL, and without a typical "dome-and-dart" feature in precordial leads. Radiofrequency applications inside the left superior pulmonary vein eliminated both atrial fibrillation and the ectopic pacemaker.     

Atypical atrial flutters.

Typical atrial flutter is due to a counterclockwise macro-re-entry circuit localized in the right atrium with a surface ECG pattern showing predominantly negative F waves in the inferior leads and positive F waves in V1. Recently it has been proposed to classify atrial flutter on the basis of its cavo-tricuspid isthmus dependence rather than on the ECG pattern. Therefore some atrial flutters are considered typical even if the ECG does not exhibit a typical pattern. This is the case for reverse typical atrial flutter, lower loop re-entry and partial-isthmus-dependent short circuit flutter. The term atypical flutter refers to a non-isthmus dependent flutter. Usually these patients have had previous cardiac surgery with a right or left atriotomy. Flutter involving a spontaneous right atrial scar is not uncommon.     

A new application of the ST-HR loop to evaluate the exercise-induced reversible ischemia in healed anterior wall myocardial infarction

Exercise-induced ST-segment elevation in infarct-related leads is often seen on the treadmill exercise electrocardiogram of patients with anterior wall myocardial infarction. However, the cause of this phenomenon is still a matter of controversy. The purpose of this study was to evaluate the relation between the direction of ST-segment-heart rate (ST-HR) loop rotation and reversible myocardial ischemia in the infarct-related area. A total of 58 patients were enrolled in this study. They had healed anterior wall myocardial infarctions with single-vessel coronary artery disease and exercise-induced ST-segment elevations in the infarct-related leads, as observed on treadmill exercise electrocardiograms. All patients underwent treadmill exercise electrocardiography and dobutamine stress echocardiography at discharge. The direction of rotation of the ST-HR loop constructed from the treadmill exercise electrocardiogram and the dobutamine stress echocardiographic findings in the infarct-related area were compared. Counterclockwise rotation was seen in 26 of 58 patients. Compared with clockwise rotation, patients with counterclockwise rotation had significantly more viable myocardium (92% vs 69%, p = 0.04) and presence of reversible myocardial ischemia (58% vs 6%, p < 0.01). On the basis of the counterclockwise rotation findings, the diagnostic value of the presence of reversible myocardial ischemia was calculated. The sensitivity, specificity, and accuracy was 88%, 73%, and 77%, respectively. Counterclockwise rotation of ST-HR loops was strongly related to reversible myocardial ischemia in the infarct-related area. In conclusion, our results have shown that analysis of ST-HR loops may be useful in evaluating the cause of exercise-induced ST-segment elevation in infarct-related leads.     

The VCG in ventricular septal defect in the first two years of life. Qualitative and quantitative analyses (author's transl)].

A group of 37 patients, less than 2 years old, with a ventricular septal defect of variable degree, and a left to right shunt, were studied by vectorcardiography. The duration, the direction and the aspect of the QRS loop on the three orthogonal planes, the voltage of the 0.01; 0.02; 0.04 vectors, the right and the left maximum spatial vectors and their projection on the H and F planes were analyzed and correlated to the right ventricular systolic pressure and Qp/Qs. A clockwise or an eight-type loop on the frontal plane, regardless of RVSP, was observed; on the H plane the loop is, usually, counterclockwise when the pressure is low or medium, and can be of the eight-type but never clockwise when the pressure is systemic. Very interestingly, the quantitative analysis showed a consistent increase of the LMSV. A progressive relationship between the spatial vectors and the right ventricular pressure was noted. The diagnosis of combined ventricular hypertrophy depend upon the following findings: the majority of cases showed a large, counterclockwise and anterior QRS loop on the H with the maximum vector to the left and anteriorly; in all cases the 0.01; 0.02; 0.04 vectors were enlarged, thus warranting the diagnosis of combined ventricular hypertrophy in the first few months of life. 4 cases with low RVSP presented increased initial forces to the right and anteriorly directed, while the major portion of the loop was in the left posterior quadrant on the H plane, with a counterclockwise direction. In our view, the differential diagnosis between this type of aspect and that of diastolic overload of the left ventricle can rest only on the increased voltage of the 0,02 vector which means both systolic and diastolic overload of the right ventricle when accompanied by an increased 0.01 vector which indicates volume overload of left ventricle. Likewise only a quantitative analysis can help in differentiating a combined ventricular hypertrophy from a normal tracing in children under 6 months who show an eight-type loop on the H plane with initial and medium vectors directed anteriorly to the left and counterclockwise, and terminal vectors to the right, posteriorly and clockwise, or in those cases with an anterior clockwise loop on the H plane. Moreover, in the first month of life, the VCG of large VSD with increased pulmonary flux and pressure, can be differentiated from the normal by the QRS loop on the H plane which is clockwise, with initial vectors directed to the left and anteriorly with increased LMSV.     

Vectorcardiographic diagnosis and electrocardiographic correlation in left ventricular asynergy due to coronary artery disease. I. Severe asynergy of the anterior and apical segments.

The transverse plane QRS loop vectorcardiogram (VCG) was analyzed in 102 consecutive patients, angiographically proven to have coronary artery disease (CAD), whose right anterior oblique left ventriculogram showed severe asynergy (akinesis or marked hypokinesis) of the anterior and apical segments. Eighty-four of the 102 loops were considered to be diagnostic of severe asynergy because similar loops were not found in patients with CAD with less severe asynergy of either or both segments or in normal control subjects. Eighty-two of the 84 showed a uniformly abnormal pattern. Posterior vectors exhibited partial or complete clockwise "rotation" and were much more prominent than early anterior forces. In fact, the latter were often absent. In the other two VCG's at least the early half of the loop displayed prominent anterior vectors. The ECGs showed marked variability of the QRS in leads V-2-V-6. Abnormal Q waves were present in only 63 of the 102. The numbers of these leads showing abnormal Q waves varied from one to all of these positions.     

The effect of digoxin on the electrocardiogram of healthy middle-aged and elderly patients at rest and during exercise--a comparison with the ECG reaction induced by myocardial ischemia

The effect of digoxin on electrocardiogram (ECG) at rest and during exercise, and on QRS amplitude variability (variance ECG) was studied in 20 healthy, middle-aged men and women. Exercise test and variance ECG were performed before and after pretreatment with digoxin orally. Plots of ST-segment level vergus heart rate (HR) were constructed from the rest and exercise ECG recordings. Thus obtained ST/HR loops were compared with loops from 10 male patients with angiographically verified ischemic heart disease (IHD). Pretreatment with digoxin caused a significant (P <.001) ST depression in precordial leads, which was similar in men and women and returned promptly to the isoelectric level after exercise resulting in a counterclockwise rotation of the ST/HR loop. In IHD patients, the exercise-induced ST-segment depression was significantly more pronounced (P <.01) and the ST-segment recovery slower, resulting in clockwise rotated ST/HR loops. The results of variance ECG were not influenced by digoxin. The digoxin-induced ST-reaction during exercise mimics exercise-induced ischemic ST-reaction in patients with IHD, but can still be discerned by the analysis of ST/HR loops.     

Activation sequence during atrial flutter in dogs with surgically induced right atrial enlargement: I. Observations during sustained rhythms

The atrial activation sequences during 15 episodes of sustained atrial flutters were determined in the isolated hearts of four dogs with surgically induced right atrial enlargement (TI/PS dogs). These sequences were compared with the activation sequences of six episodes of nonsustained atrial tachyarrhythmias induced in three control hearts. Total endocardial activation of both atria during normal sinus rhythm and during the arrhythmias was determined first by recording simultaneously from 192 pairs of recording electrodes positioned into egg-shaped electrode arrays, and then by determining the moment of activation from each of the recorded electrograms. Isochronal maps of total activation were constructed by computer. Nonsustained atrial rhythms inducible in control hearts were due to circus movement excitation either in the left atrium (two episodes) or in the right atrium (four episodes). On the other hand, all 15 episodes of sustained atrial flutter induced and mapped in the TI/PS dog hearts were due to reentrant excitation in the enlarged right atrium. The reentrant pattern could be in a clockwise or counterclockwise pattern. In these episodes of stable flutter an area of functional block was an essential component to the reentrant excitation.     

Recovery-phase patterns of ST segment depression in the heart rate domain cannot distinguish between anginal patients with coronary artery disease and patients with syndrome X

Continuous plots of ST segment depression related to heart rate during exercise and recovery (heart rate recovery loops) can differentiate patients with coronary artery disease from clinically normal subjects. To assess whether this method can also distinguish patients with angina and coronary artery disease from those with syndrome X (angina, positive exercise tests, and normal coronary arteries), we studied 75 patients with coronary artery disease and 30 patients with syndrome X. The average heart rate recovery loops for coronary artery disease and syndrome X patients followed similar counterclockwise loop rotations. Individual data analysis, however, showed that in coronary artery disease patients the loop rotation was counterclockwise in 66 (88%) and intermediate in nine (12%), while none had a clockwise loop nine (30%), and intermediate in nine (30%). Thus heart rate recovery loops cannot distinguish patients with angina and coronary artery disease from those with syndrome X.