Nagaraj Desai

Beat-to-beat heart rate and QT variability in patients with Congestive cardiac failure: Blunted response to orthostatic challenge

Background: Congestive cardiac failure is associated with increased sympathetic activity and impaired baroreflex function. We sought to test the hypothesis that these patients also have blunted response of beat‐to‐beat QT interval variability during orthostatic challenge.

Significant difference in beat-to-beat QT interval variability among different leads.

QT interval on the surface electrocardiogram (ECG) reflects the time for repolarization of myocardium, and QTc prolongation is strongly associated with sudden cardiac death. Findings of studies that have examined the dispersion of QT interval in 12-lead ECGs strongly suggest that an increased QT dispersion between different leads is associated with an increased risk of cardiac mortality. Recent studies using novel techniques on beat-to-beat QT interval variability have also shown that the interval is both influenced by the autonomic nervous system and a predictor of sudden cardiac death. However, in these studies the variability of QT was quantified in a single lead, and thus is different from QT dispersion. The present study examined whether there was a significant difference between QT variability (detrended QT variance [QTv]) and Qtvi (index of QT interval variability corrected for mean QT squared divided by heart rate variability corrected for mean heart rate squared) in 17 data sets of continuous ECGs recorded in three channels (leads V(5), V(1), and V(3)) during ambulatory monitoring of ECG digitized at 1,000 Hz. The results showed a highly significant difference between QT variability measures (QTv and QTvi) (P < 0.0001) in two of three lead configurations that were used (V(5) and V(1) versus V(3)). This finding underscores the importance of using the same lead while recording ECG for the calculation of QT variability, though further investigations are clearly warranted before any definitive conclusion can be made. These findings should be evaluated in relation to the issue of local versus global cardiac repolarization of ventricular myocardium.

Relationship between Beat‐to‐Beat Variability of RT‐Peak and RT‐End Intervals in Normal Controls, Patients with Anxiety, and Patients with Cardiovascular Disease

Background: Some studies suggest that it is important to take the end of “T” wave to quantify QT‐interval variability, which signifies cardiac repolarization lability, as there is substantial and important information beyond the peak of the T wave on the surface electrocardiogram.

Beat-to-beat QT interval variability in atrial fibrillation with and without congestive cardiac failure.

Beat-to-Beat QT Interval Variability in Atrial Fibrillation with and without Congestive Cardiac Failure Vikram K. Yeragani, M.D.,∗ Swaroop Adiga, M.B.B.S., Nagaraj Desai, M.D., D.M.,† and Ronald D. Berger, M.D., Ph.D.‡ From the ∗Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, Michigan, USA; †Department of Cardiology, M. S. Ramaiah Medical College Hospital, Bangalore, India; and ‡Department of Cardiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA

Increased Chaos of Beat-to-Beat QT Interval Variability in Patients with Congestive Cardiac Failure: Decreased Chaos of QT with Clinical Improvement

There is increasing evidence supporting the additional utility of nonlinear techniques such as chaos analysis of heart rate (HR) time series as indictors of prognosis in cardiac patients. Prolongation of rate-corrected QT interval, QTc, is strongly associated with sudden cardiac death. Recent studies of beat-to-beat QT interval variability (QTV) have shown that an increase in QTV is associated with increased sympathetic activity. QTvi, a QT variability index (QT variance corrected for mean QT divided by HR variance corrected for mean HR), is also a predictor of sudden cardiac death. We studied the utility of a measure of chaos, the Largest Lyapunov Exponent (LLE) of beat-to-beat HR and QT time series at baseline and after treatment in patients with congestive heart failure (CHF). We compared beat-to-beat HR and QT interval data in 23 patients with CHF and 19 age-matched normal controls. The ECG data were acquired in lead II configuration at a sampling rate of 1000 Hz. CHF patients had a significantly lower LLE of HR and a significantly higher LLE of QT time series than did normal controls. Clinical improvement in a subgroup of these patients was associated with a decrease in QT-LLE and a decrease in LLEqthr (LLE-QT/LLE-HR). These results demonstrate a decreased chaos of HR and increased chaos of QT time series in patients with CHF suggesting decreased cardiac vagal and increased sympathetic function in patients with CHF. Nonlinear measures may prove to be of additional utility to linear measures as surrogate end points to evaluate treatment effect in these patients.

A Study to derive distribution of carotid intima media thickness and to determine its COrrelation with cardiovascular Risk factors in asymptomatic nationwidE Indian population (SCORE-India)

Background There is presently no data to describe normal distribution of carotid intima-media thickness (CIMT), an established measure of subclinical atherosclerosis, in Indian subjects. Methods In this multi-centric study, 1229 subjects with age ≥30 years and no previous cardiovascular disease (CVD) underwent CVD risk factor assessment and CIMT measurement. Mean far wall common carotid artery IMT was measured on both sides and averaged. Results Mean age of the subjects was 48.0 ± 12.0 years and 54.2% were men. CIMT measurement was feasible in 1157 subjects. Mean, median and 75th percentile values of CIMT for different age-groups were derived for men and women separately. There was a progressive increase in CIMT with increasing age (P < 0.001) and men had higher CIMT values than women (0.608 ± 0.12 mm vs. 0.579 ± 0.11 mm, P < 0.001). The CIMT values were also higher in diabetics (0.635 ± 0.10 mm) and hypertensives (0.624 ± 0.10 mm) as compared to non-diabetics (0.589 ± 0.12 mm, P < 0.001) and non-hypertensives (0.592 ± 0.12, P 0.02) respectively. Among continuous variables, age, systolic blood pressure and fasting blood glucose had strong to modest correlation with CIMT (Pearsons r 0.524, 0.282 and 0.192 respectively, all P values <0.001), whereas body mass index, diastolic blood pressure and serum triglycerides exhibited weak but still statistically significant relationship (Pearsons r 0.069, P 0.019; Pearsons r 0.065, P 0.026; and Pearsons r 0.094, P 0.001, respectively). Conclusions This is the first study to provide age- and gender-specific distribution of CIMT in Indian subjects free from CVD. This information should help facilitate further research and clinical work involving CIMT in India.

The Indian Consensus Document on cardiac biomarker

Despite recent advances, the diagnosis and management of heart failure evades the clinicians. The etiology of congestive heart failure (CHF) in the Indian scenario comprises of coronary artery disease, diabetes mellitus and hypertension. With better insights into the pathophysiology of CHF, biomarkers have evolved rapidly and received diagnostic and prognostic value. In CHF biomarkers prove as measures of the extent of pathophysiological derangement; examples include biomarkers of myocyte necrosis, myocardial remodeling, neurohormonal activation, etc. In CHF biomarkers act as indicators for the presence, degree of severity and prognosis of the disease, they may be employed in combination with the present conventional clinical assessments. These make the biomarkers feasible options against the present expensive measurements and may provide clinical benefits.