István Préda

A computer heart model incorporating anisotropic propagation. II. Simulations of conduction block.

This study describes the simulation of the more common types of conduction blocks with a computer model of the heart incorporating anisotropic propagation. The rationale was to test the model as to its ability to simulate these blocks by physiologically justifiable adjustments of the conduction system alone. The complete blocks were generated by simply blocking conduction totally at selected sites in the proximal conduction system, and the incomplete blocks by slowing down the conduction velocity in the proximal system. Also simulated were the left fascicular blocks and the bilateral blocks. All simulated electrocardiograms, vectorcardiograms, body surface potential maps, and epicardial isochrones for these blocks were similar to clinically observed data, with the exception of the left posterior hemiblock, which was slightly atypical. This could be because such blocks are usually accompanied by other cardiac pathologies not included in our simulations. The model also supports van Dams observation that during left bundle branch block the passage of activation from right to left occurs via slow myocardial activation with no evidence of a local delay due to a septal barrier. Finally, the model suggests that a left bundle branch block with a normal frontal plane QRS axis may simply represent a case of an incomplete left bundle block, whereas one that exhibits a left axis QRS deviation in the frontal plane represents a more severe complete left bundle branch block.

QRS alterations in body surface potential distributions during percutaneous transluminal coronary angioplasty in single-vessel disease*

Body surface QRS potentials were recorded with 63 chest leads in 20 patients with proximal single-vessel disease located on either the left anterior descending coronary artery (n = 10), the right coronary artery (n = 6), or the left circumflex coronary artery (n = 4) before, during, and after percutaneous transluminal coronary angioplasty. In each case, three consecutive inflations of relatively short duration (37 +/- 14 seconds) were carried out. Electrical activity was displayed as unipolar electrograms and body surface potential maps. The total QRS complex duration decreased in 14 of the 20 patients. Focal conduction disturbances were observed in six cases; all six had left anterior descending coronary artery occlusion and two were also accompanied by a clear shortening of the right epicardial breakthrough time. In these two cases, an initial activation loss seemed to be characteristic, whereas in the other four cases, a rather diffuse slowing of intraventricular conduction, especially during the terminal portion of the QRS, could be observed. Individual and group mean isointegral difference body surface potential maps (during-minus-before dilation) were considered valuable for the interpretation of localized changes in intraventricular conduction during percutaneous transluminal coronary angioplasty, and their individual variations could, at least partly, be explained by the presence or absence of collateral circulation. Two different hypotheses are suggested to account for the QRS complex shortening observed during short-term myocardial ischemic injury: (1) coronary artery occlusion delayed activation of the portion of the septal region that is normally activated early during the QRS, and/or (2) coronary artery occlusion increased the speed of propagation within the ventricles. Both of these hypotheses are discussed in light of earlier clinical and experimental results.

High on clopidogrel treatment platelet reactivity is frequent in acute and rare in elective stenting and can be functionally overcome by switch of therapy

UNLABELLEDnThe benefit of adjusted antiplatelet therapy in patients with myocardial infarction after primary percutaneous coronary intervention is not well elucidated. We aimed to identify patients with high on treatment platelet reactivity and to gradually adjust antiplatelet therapy.nnnMATERIALS AND METHODSnWe enrolled 133 acute myocardial infarction and 67 stable angina patients undergoing intracoronary stenting into our study. Maximal aggregation was determined with light transmission aggregometry. Aggregation >50% induced by 5 μM ADP was indexed with high on-clopidogrel treatment platelet reactivity. In these cases 75 mg clopidogrel was doubled and control test was performed. Patients effectively inhibited with 150 mg clopidogrel were defined as clopidogrel pseudo non-responders. Patients with high platelet reactivity even on 150 mg clopidogrel were considered as clopidogrel real non-responders and were switched to ticlopidine.nnnRESULTSnAggregations (5ADP; p=0.046) and the ratio of real non-responders (p=0.013) were significantly higher in the myocardial infarction group. Most real non-responders were effectively treated with switch of therapy. The ratio of pseudo non-responders also tended to be higher in myocardial infarction. Platelet reactivity remained constant during follow-up; however, a new appearance of high platelet reactivity was observed at 6 and at 12 months.nnnCONCLUSIONSnPatients with acute myocardial infarction undergoing percutaneous coronary intervention may benefit from prospective platelet function testing, because of higher platelet reactivity and much higher ratio of clopidogrel real non-response. Switch of therapy may effectively overcome clopidogrel non-response. A new appearance of high platelet reactivity with unknown clinical significance is observed in both groups among the patients on clopidogrel.

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.

Diagnostic value of body surface potential mapping in assessment of the coronary artery lesion after angina pectoris and without repolarization changes on the electrocardiogram

BACKGROUNDnThe body surface potential mapping (BSPM) method is sensitive in detecting minor electrical potential abnormalities, but its diagnostic value is unclear in detection and localization of significant coronary artery lesion (CAL) in patients after angina pectoris and without ischemic electrocardiogram abnormalities at the time of the BSPM record.nnnMETHODS AND RESULTSnCharacteristic features and quantitative parameters of the isopotential maps during the depolarization were evaluated and compared with the result of coronary angiography in 228 patients (164 males; age, 61.6 +/- 9.5 years). Twenty-three of them had their first angina, but the others had a history of earlier angina, unstable angina, non-ST-elevation infarction. Fifty-nine healthy subjects (32 males; age, 53.3 +/- 12.2 years) served as control. The diagnostic power was high in detection of CAL among patients with previous ischemic events, but it was low in first angina. The accuracy of the CAL localization by multiple regression was different: at 90% specificity level, the sensitivity was near 80% for right/posterior descending CAL and slightly more than 60% for left anterior descending CAL but only 19% for first marginal/first diagonal CAL.nnnCONCLUSIONSnThe BSPM changes during the depolarization could well indicate CAL only after previous ischemic events. Sensitivity and specificity of the CAL localization depended on the extension and location of the underlying myocardium damage.

Diagnostic value of the left atrial electrical potentials detected by body surface potential mapping in the prediction of coronary artery disease

BACKGROUNDnThe electrocardiographic diagnosis of significant coronary artery stenosis (CAD) is often based on the investigation of the left ventricular repolarization changes during exercise ECG stress test (EST). Our aim was to prove that the electric activity of the left atrium can indicate the ischemic damage of the left ventricle, and furthermore, it is able to indicate CAD without exercise.nnnMETHODS AND RESULTSnPatients with chest complaints but without evidence of acute coronary syndrome were investigated by EST and body surface potential mapping (BSPM, 63 leads). CAD was proven in 45 cases (32 men, years 40-76) and excluded in 50 cases (35 men, years 38-72) with coronary angiography. Left atrial electric potentials (EP-LA) before and after 0.08 mg sublingual nitroglycerine administration differed significantly (p<0.001) in the two groups. According to Fischer linear discriminant analysis, this difference in % (EP-LA(d%)) was the best separating parameter: below limit of -14.17% (CAD prevalence was considered) this parameter predicted CAD with 93% sensitivity, 100% specificity, >10 positive and 0.05 negative likelihood ratio (weighted for prevalence). The EST predicted CAD with 71% sensitivity, 78% specificity, 2.43 positive and 0.28 negative likelihood ratios.nnnCONCLUSIONnThe electrical activity changes of the left atrium seemed to be suitable to predict CAD as an EST-alternative resting method.

A Simple Numerical Body Surface Mapping Parameter Signifies Successful Percutaneous Coronary Artery Intervention

In coronary artery disease (CAD), body surface potential mapping (BSPM) may reveal minor electrical potential changes appearing in the depolarization phase even if pathological changes are absent on the conventional 12‐lead ECG. We hypothesized that a simple BSPM parameter, Max/Min signifies successful percutaneous coronary intervention (PCI).

Non-invasive, Complex Examination of Micro- and Macrovascular System of Patients with Type 1 Diabetes Mellitus with or Without Vascular Complications

Abstract Objective: We examined the vascular system, from the microvasculature to the aorta, in diabetes mellitus, using non-invasive methods. Methods: We enrolled patients with type 1 diabetes: 17 patients without complications (DMW) and 19 patients with clinically manifest complications (DMC). Control group was represented by 34 healthy volunteers (C). We examined microvascular function with laser-Doppler flowmetry, using post-occlusive reactive hyperemia test and local heating. Arterial stiffness was studied by arteriograph, determining augmentation index and pulse wave velocity. We measured serum levels of sE-selectin and sICAM-1, markers of endothelial dysfunction. Results: Microvascular reactivity was significantly reduced in DMC-, and tendentiously in DMW groups. sE-selectin level was significantly higher in DMC group than in controls. Arterial stiffness was the highest in the DMC group and the lowest in the DMW group. Heart rate was significantly higher in both diabetic groups compared to controls. Time to maximum flow during PORH test tended to be the shortest in DMW group. Conclusions: Our results confirm impairment of the microvascular system in diabetic patients, even in early, uncomplicated stage of the disease, and might demonstrate diffuse hyperkinesis in the vascular system, resulting from the insulin effect or refering to the “vasodilation phase” of diabetes mellitus.