Sinisa Pavlovic

Myocardial mechanical and QTc dispersion for the detection of significant coronary artery disease

AIMS Ischaemic but viable myocardium may exhibit prolongation of contraction and QT interval duration, but it is largely unknown whether non-invasive assessment of regional heterogeneities of myocardial deformation and QT interval duration could identify patients with significant coronary artery disease (CAD). METHODS AND RESULTS We retrospectively studied 205 patients with suspected CAD who underwent coronary angiography. QTc dispersion was assessed from a 12-lead electrocardiogram (ECG) as the difference between the longest and shortest QTc intervals. Contraction duration was assessed as time from the ECG R-(Q-)wave to peak longitudinal strain in each of 18 left ventricular segments. Mechanical dispersion was defined as either the standard deviation of 18 time intervals (dispersionSD18) or as the difference between the longest and shortest time intervals (dispersiondelta). Longitudinal strain was measured by speckle tracking echocardiography. Mean contraction duration was longer in patients with significant CAD compared with control subjects (428 ± 51 vs. 410 ± 40 ms; P = 0.032), and it was correlated to QTc interval duration (r = 0.47; P < 0.001). In contrast to QTc interval duration and dispersion, both parameters of mechanical dispersion were independently associated with CAD (P < 0.001) and had incremental value over traditional risk factors, wall motion abnormalities, and global longitudinal strain (GLS) for the detection of significant CAD. CONCLUSION The QTc interval and myocardial contraction duration are related to the presence of significant CAD in patients without a history of previous myocardial infarction. Myocardial mechanical dispersion has an incremental value to GLS for identifying patients with significant CAD.

EYE LENS EXPOSURE TO MEDICAL STAFF PERFORMING ELECTROPHYSIOLOGY PROCEDURES: DOSE ASSESSMENT AND CORRELATION TO PATIENT DOSE

The purpose of this study was to assess the patient exposure and staff eye dose levels during implantation procedures for all types of pacemaker therapy devices performed under fluoroscopic guidance and to investigate potential correlation between patients and staff dose levels. The mean eye dose during pacemaker/defibrillator implementation was 12 µSv for the first operator, 8.7 µSv for the second operator/nurse and 0.50 µSv for radiographer. Corresponding values for cardiac resynchronisation therapy procedures were 30, 26 and 2.0 µSv, respectively. Significant (p < 0.01) correlation between the eye dose and the kerma-area product was found for the first operator and radiographers, but not for other staff categories. The study revealed eye dose per procedure and eye dose normalised to patient dose indices for different staff categories and provided an input for radiation protection in electrophysiology procedures.

The Relationship of Myocardial Collagen Metabolism and Reverse Remodeling after Cardiac Resynchronization Therapy

Summary Background: In the majority of patients with a wide QRS complex and heart failure resistant to optimal medical therapy, cardiac resynchronization therapy (CRT) leads to rever se ventricular remodeling and possibly to changes in cardiac collagen synthesis and degradation. We investigated the relationship of biomarkers of myocardial collagen meta bolism and volumetric response to CRT. Methods: We prospectively studied 46 heart failure patients (mean age 61±9 years, 87% male) who underwent CRT im plantation. Plasma concentrations of amino-terminal pro peptide type I (PINP), a marker of collagen synthesis, and carboxy-terminal collagen telopeptide (CITP), a marker of collagen degradation, were measured before and 6 months after CRT. Response to CRT was defined as 15% or greater reduction in left ventricular end-systolic volume at 6-month follow-up. Results: Baseline PINP levels showed a negative correlation with both left ventricular end-diastolic volume (r=−0.51; p=0.032), and end-systolic diameter (r=−0.47; p=0.049). After 6 months of device implantation, 28 patients (61%) responded to CRT. No significant differences in the base-line levels of PINP and CITP between responders and nonresponders were observed (p>0.05 for both). During follow-up, responders demonstrated a significant increase in serum PINP level from 31.37±18.40 to 39.2±19.19 μg/L (p=0.049), whereas in non-responders serum PINP levels did not significantly change (from 28.12±21.55 to 34.47±18.64 μg/L; p=0.125). There were no significant changes in CITP levels in both responders and non-responders (p>0.05). Conclusions: Left ventricular reverse remodeling induced by CRT is associated with an increased collagen synthesis in the first 6 months of CRT implantation.

Uncoupling of cardiac and respiratory rhythm in atrial fibrillation

Abstract Rearranged origin of heart rhythm in patients with atrial fibrillation (AF) influences the regulation of the heart and consequently the respiratory rhythm, and the bidirectional interaction of these rhythms not documented. Hence, we examined coupling of the RR interval and the respiration (Resp) signal by coherence, Granger causality and the cross-sample entropy method of time series analysis in patients with AF and a healthy control group. In healthy subjects, the influence of respiration on cardiac rhythm was found as increased coherence at the breathing frequency (BF) range, significantly stronger interaction and synchrony from Resp to RR than from RR to Resp. On the contrary, in patients with AF, coherence at BF diminished, there were no causal interactions between signals in both directions, which resulted in equally great asynchrony between them. In AF, the absence of full functionality of the sinoatrial node, as an integrator of neural cardiac control, resulted in diminished vagal modulation of heart periods and consequently impaired bidirectional cardio-respiratory interaction.

Bidirectional Cardio-Respiratory Interactions in Heart Failure

We investigated cardio-respiratory coupling in patients with heart failure by quantification of bidirectional interactions between cardiac (RR intervals) and respiratory signals with complementary measures of time series analysis. Heart failure patients were divided into three groups of twenty, age and gender matched, subjects: with sinus rhythm (HF-Sin), with sinus rhythm and ventricular extrasystoles (HF-VES), and with permanent atrial fibrillation (HF-AF). We included patients with indication for implantation of implantable cardioverter defibrillator or cardiac resynchronization therapy device. ECG and respiratory signals were simultaneously acquired during 20 min in supine position at spontaneous breathing frequency in 20 healthy control subjects and in patients before device implantation. We used coherence, Granger causality and cross-sample entropy analysis as complementary measures of bidirectional interactions between RR intervals and respiratory rhythm. In heart failure patients with arrhythmias (HF-VES and HF-AF) there is no coherence between signals (p < 0.01), while in HF-Sin it is reduced (p < 0.05), compared with control subjects. In all heart failure groups causality between signals is diminished, but with significantly stronger causality of RR signal in respiratory signal in HF-VES. Cross-sample entropy analysis revealed the strongest synchrony between respiratory and RR signal in HF-VES group. Beside respiratory sinus arrhythmia there is another type of cardio-respiratory interaction based on the synchrony between cardiac and respiratory rhythm. Both of them are altered in heart failure patients. Respiratory sinus arrhythmia is reduced in HF-Sin patients and vanished in heart failure patients with arrhythmias. Contrary, in HF-Sin and HF-VES groups, synchrony increased, probably as consequence of some dominant neural compensatory mechanisms. The coupling of cardiac and respiratory rhythm in heart failure patients varies depending on the presence of atrial/ventricular arrhythmias and it could be revealed by complementary methods of time series analysis.

Knowledge management system for clinical decision support — Application in cardiology

Clinical decision support systems have been recognized as promising tools for influencing healthcare provider performance to improve and streamline the quality of healthcare delivery. In this paper we present the knowledge management module, developed as part of KardioNet system, aimed to provide clinical decision making support for treatment of patients with Acute Coronary Syndrome.