Electrophysiological mechanisms of the SI SII SIII electrocardiographic morphology

The S1S2S3 electrocardiographic pattern - Prevalence and relation to cardiovascular and pulmonary diseases in the general population

BACKGROUND

There is lack of studies exploring the incidence and association with diseases of the S1S2S3 electrocardiogram (ECG) pattern in the general population.

SUBJECTS AND METHODS

This population study included 6299 individuals aged 30+, and explored the prevalence and association between S1S2S3 and cardiovascular and pulmonary diseases. Criteria for the S1S2S3-I and S1S2S3-II ECG pattern were fulfilled when there was an S wave in the leads I, II and III, and the S-wave amplitude was greater than the R-wave amplitude in one or two of the leads, respectively.

RESULTS

The S1S2S3-I ECG pattern was found in 2332 subjects (36.9%). After age adjustment, hypertension was associated with S1S2S3-I (Odds ratio [OR] 1.25, 95% CI 1.12-1.41, p < 0.001). This age-adjusted association was statistically significant among men but not among women (OR 1.37, 1.16-1.62, p < 0.001 and OR 1.13, 0.97-1.33, p = 0.126, respectively). The S1S2S3-II ECG pattern was present in 193 subjects (3.1%). After age adjustment, heart failure proved to be associated with S1S2S3-II (OR 1.85, 1.18-2.90, p = 0.007). Dividing the population by sex, resulted in a statistically significant age-adjusted association for men but not for women (OR 2.30, 1.22-4.33, p = 0.010 and OR 1.59, 0.83-3.03, p = 0.159, respectively). Interactions with sex were statistically non-significant.

CONCLUSION

In the general adult population, the prevalence of the S1S2S3 ECG pattern is markedly affected by the diagnostic ECG criteria. The S1S2S3-I pattern was associated with hypertension, while S1S2S3-II was associated with heart failure, and both associations were enhanced in men. The associations with other studied cardiovascular and pulmonary diseases were minor and not clinically useful for risk stratification.

Prediction of ventricular tachyarrhythmia in Brugada syndrome by right ventricular outflow tract conduction delay signs

BACKGROUND

Brugada syndrome (BrS) is an autosomal dominant disease responsible for sudden cardiac death in young individuals without structural anomalies. The most critical part in the management of this channelopathy is identification of high-risk patients, especially asymptomatic subjects. Prior studies have shown that conduction delay in the right ventricular outflow tract (RVOT) is the main mechanism for developing ventricular tachyarrhythmia (VTA) in BrS patients. The aim of this study was to investigate the significance of electrocardiographic RVOT conduction delay parameters as predictors for development of VTA in patients with BrS.

METHODS AND RESULTS

We retrospectively analyzed electrocardiograms obtained from 147 BrS patients (43 ± 15 years, 65% men) and assessed the following electrocardiographic parameters: (1) Tzou criteria (V1R > 0.15 mV, V6S > 0.15 mV, and V6S:R > 0.2), (2) prominent S wave in lead I, lead II, and lead III, (3) SII > SIII, and (4) prominent Q wave in lead III as possible predictors of VTA occurrences during follow-up. Prominent SI, SII, SIII, SII > SIII, QIII, and +ve Tzou criteria occurred more frequently in patients who either presented with VTA or developed VTA during the follow-up of 56 (IQR: 40-76) months. SII > SIII has the highest area under the curve for prediction of VTA (AUC: 0.84, sensitivity: 80%, specificity: 89%). Multivariable regression analysis showed that prominent S waves in lead I, SII > SIII and +ve Tzou criteria are independent predictors for VTA in BrS patients.

CONCLUSION

Prominent S in lead I, SII > SIII and +ve Tzou criteria can be used as effective signs for predicting VTA in patients with BrS.

Electrocardiographic manifestation of the middle fibers/septal fascicle block: a consensus report

There are fibers in the left ventricle (LV) (LV middle network) that in around one third of cases may be considered a true septal fascicle that arises from the common left bundle. Its presence and the evidence that there are 3 points of activation onset in the LV favor the quadrifascicular theory of the intraventricular activation of both ventricles. Since the 70s, different authors have suggested that the block of the left middle fibers (MS)/left septal fascicle may explain different electrocardiographic (ECG) patterns. The 2 hypothetically based criteria that are in some sense contradictory include: a) the lack of septal "q" wave due to first left and later posteriorly shifting of the horizontal plane loop and b) the presence of RS in lead V(2) (V(1)-V(2)) due to some anterior shifting of the horizontal plane vectorcardiogram loop. However, there are many evidence that the lack of septal q waves can be also explained by predivisional first-degree left bundle-branch block and that the RS pattern in the right precordial leads may be also explained by first-degree right bundle-branch block. The transient nature of these patterns favor the concept that some type of intraventricular conduction disturbance exists but a doubt remains about its location. Furthermore, the RS pattern could be explained by many different normal variants. To improve our understanding whether these patterns are due to MF/left septal fascicle block or other ventricular conduction disturbances (or both), it would be advisable: 1) To perform more histologic studies (heart transplant and necropsy) of the ventricular conduction system; 2) To repeat prior experimental studies using new methodology/technology to isolate the MF; and 3) To change the paradigm: do not try to demonstrate if the block of the fibers produces an ECG change but to study with new electroanatomical imaging techniques, if these ECG criteria previously described correlate or not with a delay of activation in the zone of the LV that receives the activation through these fibers or in other zones.

Increase in the QRS duration after amelioration of peripheral edema and after hemodialysis

Association among weights, amplitude of QRS complexes, and QRS duration in patients with peripheral edema has been described. This study explored whether increase in QRS duration occurs with amelioration of peripheral edema or after hemodialysis. Sums of the amplitudes of the 12 electrocardiographic leads and corresponding QRS duration were measured in 12 patients with peripheral edema before and after loss of weight, in 28 patients with a critical illness but without change in their weight ("controls"), and in 1 patient before and after hemodialysis. QRS duration increased from 90.1+/-25.0 milliseconds to 101.7+/-25.8 milliseconds (P=.001) in patients with peripheral edema, was unchanged in the controls, and increased from 87.8+/-5.9 milliseconds before to 92.7+/-6.7 milliseconds after hemodialysis (P=.007). It is proposed that these increases in QRS duration are only apparent (not electrophysiologically real), representing an extracardiac phenomenon mediated by alterations in the composite impedance of the passive body volume conductor, resulting in measurement of augmented QRS complexes after fluid removal. The clinical implications for patients with congestive heart failure are discussed.

Connection between right ventricular pressure and the ECG

According to the literature, electrocardiographic signs of right ventricular hypertrophy have low sensitivity. The cause of this low sensitivity may be attributed to the original studies that were performed mostly in children with hypoplastic left ventricles or congenital heart abnormalities. In adulthood cases of normal or hypertrophic left ventricles, electrocardiographic right ventricular hypertrophy can only be detected during the late phase of ventricular depolarization. Two hundred four adult cardiac patients with complete noninvasive and invasive records were systematically studied by conventional and vectocardiographic methods. The terminal QRS (S wave) of the standard lead I has proved to be informative for detecting electrocardiographic signs in the presence of elevated right ventricular pressure. In cases of chronic right ventricular pressure overload (right ventricular hypertrophy) the terminal depolarization QRS vectors pointed posteriorly and to the right; therefore, a characteristic terminal S wave was represented in the standard lead I. If right and left ventricular hypertrophy were simultaneously present, the same resultant vectors pointed posteriorly and slightly to the left. In these cases, notching of the declining phase of the R wave was frequent, and a flatness of the terminal R wave portion was characteristic. The latter electrocardiographic sign has been called "simultaneous overloading of both ventricles" by the authors. The clinical utility of the new signs have also been proved by statistical methods.

The electrocardiogram in chronic obstructive pulmonary disease

The electrocardiogram is often abnormal in patients who have chronic obstructive pulmonary disease. The most frequent abnormalities are a rightward P-wave axis (greater than or equal to 70 degrees) and a rightward QRS axis (greater than or equal to 90 degrees). In addition, low voltage in the limb leads, an S1S2S3 pattern, poor R-wave progression, a posterior-superior terminal QRS vector or other changes may be present. Transient atrial and ventricular dysrhythmias are common. Knowledge of the usual electrocardiographic manifestations of chronic obstructive pulmonary disease enables the clinician to recognize uncharacteristic abnormalities, which often represent the effects of superimposed illnesses or drug toxicity.