Biomedical subjects

Vito Starc

Publications and source records attributed to Vito Starc.

8 recordsLinked to original sources

PubMed2006

Continuous axial contraction wave in the free wall of the guinea pig left ventricle.

We studied the variation from the simultaneous contraction of the normal left ventricle (LV). The pattern of the contraction along the LV long axes was assessed on the LV free wall on seven guinea pig hearts in situ with ultra fast video system and epicardial markers by means of the latitude and the size of the areas defined by markers. We found that the contraction occurs as a continuous contraction wave from the apex towards the base, which might yield functional adaptation of these two regions to diastolic and systolic function, respectively.

Animals↗

PubMed2006

Real-time multichannel system for beat-to-beat QT interval variability.

The measurement of beat-to-beat QT interval variability (QTV) shows clinical promise for identifying several types of cardiac pathology. However, until now, there has been no device capable of displaying, in real time on a beat-to-beat basis, changes in QTV in all 12 conventional leads in a continuously monitored patient. Although several software programs have been designed to analyze QTV, heretofore, such programs have all involved only a few channels (at most) and/or have required laborious user interaction or offline calculations and postprocessing, limiting their clinical utility. This article describes a PC-based electrocardiogram software program recently codeveloped by our laboratories that, in real time, acquires, analyzes, and displays QTV in each of the 8 independent channels that constitute the 12-lead conventional electrocardiogram. The system also analyzes and displays the QTV from QT-interval signals that are derived from multiple channels and from singular value decomposition such that the effect of noise and other artifacts on the QTV results are substantially reduced compared with existing single-channel methods.

Algorithms↗

PubMed2005

Atorvastatin therapy increases heart rate variability, decreases QT variability, and shortens QTc interval duration in patients with advanced chronic heart failure.

BACKGROUND: Although statins decrease the incidence of ventricular arrhythmias in patients with atherosclerotic heart disease, their potential antiarrhythmic effects in heart failure remain undefined. METHODS AND RESULTS: Of 80 heart failure patients enrolled, 40 were randomized to receive atorvastatin (statin group); the remaining 40 served as controls. At baseline and after 3 months, we measured heart rate variability (HRV), QT variability (QTV), and QTc interval using interactive high-resolution electrocardiogram analysis. The 2 groups did not differ in baseline HRV standard deviation of normal-to-normal intervals (SDNN) (RR): 24.6 +/- 2.8 ms in statin group versus 24.8 +/- 3.1 ms in controls, P = .72; square root of the mean of squared differences between successive intervals (rMSSD) (RR): 21.2 +/- 2.7 ms versus 21.7 +/- 2.9 ms, P = .43), QTV SDNN (QT): 6.4 +/- 1.5 ms versus 6.4+/-1.7, P = .96; rMSSD QT): 9.0 +/- 2.4 ms versus 8.7 +/- 2.9 ms, P = .65, and QTc interval 450 +/- 30 ms versus 446 +/- 27 ms, P = .59. At 3 months, the statin group displayed higher HRV SDNN RR): 27.2 +/- 4.9 ms versus 24.4 +/- 2.8 ms in controls, P = .003; rMSSD RR: 24.7 +/- 4.2 ms versus 21.3 +/- 5.6 ms, P = .004, lower QTV SDNN (QT): 5.1 +/- 1.9 ms versus 6.5 +/- 2.1, P = .004; rMSSD (QT): 6.6 +/- 2.8 ms versus 8.8 +/- 3.1 ms, P = .002, and shorter QTc interval 437 +/- 29 ms versus 450 +/- 25 ms, P = .03 than the control group. CONCLUSIONS: Atorvastatin increases HRV, decreases QTV, and shortens QTc interval, and may thereby reduce the risk of arrhythmias in patients with advanced heart failure.

Anti-Arrhythmia Agents↗

PubMed2005

The video technique developed for measuring epicardial strains on guinea pig's left ventricle.

Single-plain video used for measurements of epicardial strains is a technique that yields minor interference with the studied mechanical properties of the ventricle. Due to its low temporal resolution, the existing technique is, however, not appropriate for small animals. We questioned whether the technique could be improved enough to cope with higher heart rates and miniaturization necessary for experiments on rats, mice and guinea pigs. Therefore, we developed a high-speed video system and used it for measuring epicardial strains in guinea pig hearts in situ with the open chest. The improvement was achieved in video hardware (camera: Dalsa D6-0256; framegraber: EPIX PIXCI D32) and software, the markers (glowing acrylate crystals; diameter approximately 0.15 mm) and illumination (UVA light, OSRAM L). Three markers were attached onto the epicardium in the equatorial region of the left ventricular free wall, 1.5 mm apart, with fibrin glue. From their coordinates, we calculated two-dimensional finite strains with end diastole as the reference point. The accuracy of the displacement measurement of the technique and the error introduced by approximate-visual estimation of the left ventricle coordinate system were evaluated. The accuracy of the displacement measurement was +/-1.6 microm and the temporal resolution was 2 ms. Error due to approximate coordinate system orientation was +/-3% of the strain amplitude. The typical amplitude of strains was -0.06, -0.11 and 0.04 in circumferential, axial direction and in-plane shear, respectively. The improvements enable us to perform physiologically relevant measurements of epicardial deformations on guinea pig heart.

Animals↗

PubMed2005

Coronary artery disease alters ventricular repolarization dynamics in type 2 diabetes.

Ventricular repolarization dynamics (VRD) is an important predictor of outcome in diabetes. We examined the potential impact of coronary artery disease (CAD) on VRD in type 2 diabetic patients. We recorded 5-minute high-resolution resting electrocardiograms in 38 diabetic patients undergoing elective coronary angiography, and in 38 age- and gender-matched apparently healthy subjects (controls). Using leads-I and -II, time-domain indices of VRD were calculated. Coronary angiography was regarded as positive if >/= 50% stenosis was found. Angiography was positive in 21 diabetic patients (55%). Patients with CAD had a significantly higher degree of VRD than controls (SDNN(QT): 15.81 +/- 7.22 ms versus 8.94 +/- 6.04 ms; P < 0.001, rMSSD(QT): 21.02 +/- 7.07 ms versus 11.18 +/- 7.45 ms; P < 0.001). Ventricular repolarization dynamics in diabetic patients with negative angiograms did not differ from VRD in controls (SDNN(QT): 8.94 +/- 6.04 ms versus 7.44 +/- 5.72 ms; P = 0.67, rMSSD(QT): 11.18 +/- 7.45 ms versus 10.22 +/- 5.35 ms; P = 0.82). CAD increases VRD in patients with type 2 diabetes. Therefore, changes in ventricular repolarization in diabetic patients may be due to silent CAD rather than due to diabetes per se.

Case-Control Studies↗

PubMed2005

Gender differences in knee kinematics and its possible consequences.

AIM: To analyze anatomic and kinematic characteristics of male and female knees in the sagittal plane. METHODS: Ten healthy male and 10 healthy female participants performed extension of their right lower leg in non-weight bearing and weight bearing conditions. The centers of knee joint motion were obtained by videographic motion analysis, and radii of condylar curves were calculated from digitalized X-ray scan. The Knee Roll software was made for this purpose. RESULTS: The extension of the knee in non-weight loaded and weight loaded conditions is a combination of rolling and sliding joint surface motion with 6:5 ratio, in both genders. During the last 20 degrees of the extension of weight loaded male knee, rolling/sliding ratio changed to 8:1 (P<0.05). Average radii of condylar curves were between 4.5 and 1.7 cm medially, and between 3.2 and 1.8 cm laterally, for 0 degrees and 90 degrees flexion contact point, respectively. Gender differences in the radii of condylar curves, after the adjusting to body height were insignificant. CONCLUSION: A higher proportion of joint surface sliding with consecutive anterior tibial displacement in women indicates more strain during knee extension, potentially making the female anterior cruciate ligament tend and susceptible to injury. The gender differences in the knee kinematics are probably the consequence of different soft tissue structure or its activity, because no difference in the sagittal shape of femoral condyles was noted.

Adult↗

PubMed2004

Contraction wave in axial direction in free wall of guinea pig left ventricle.

Mechanical activation of the normal left ventricle (LV) is not simultaneous; however, the potential consequences of the ejection function of the ventricle are not entirely known. We studied contraction of the LV free wall to determine whether it reveals a contraction wave in the axial direction during ejection. Seven guinea pig hearts in situ were studied via thoracotomy. In each heart, the ventricular and aortic pressures were measured by two microtipped manometers (2-Fr, Millar). Contraction of the LV free wall was assessed with a video system (Dalsa D6-0256 camera and EPIX PIXCI D32 frame grabber; acquisition rate, 500 frames/s), and 15-18 epicardial markers were used to divide the region into 20-25 triangular areas. The area sizes were studied during contraction to locate the position of the contraction wave. For each triangular area, two variables were determined as follows: the time (t(c)) from the end of diastole until the size of the area reached 80% of maximum size reduction (normalized with the duration of systole) and the normalized latitude (L(ax)) of the area (determined at the end of diastole). A relationship between these two variables was determined by regression analysis. We found that the t(c) at which the contraction wave reached a triangular area was in positive correlation with the L(ax) value for that triangular area with a slope of 0.25 +/- 0.09 and a linear correlation coefficient of 0.41 +/- 0.08. Thus contraction in the guinea pig LV free wall occurs progressively from apex to base with successive areas reaching 80% contraction.

Animals↗

PubMed2003

Atrioventricular conduction variability in coronary patients.

Variability in atrioventricular (AV) conduction has been described in healthy subjects, whereas data for coronary patients are lacking. This study was designed to evaluate AV conduction variability in patients with stable coronary artery disease. Beat-to-beat PR interval variability with 5-minute resting high-resolution electrocardiogram recordings was measured in 30 men (mean age 50.9 years) with effort angina pectoris and 30 age-matched men without clinically evident coronary artery disease (controls). To evaluate the degree of coronary artery disease in coronary patients, coronary angiography was performed. Coronary patients displayed significantly lower values of PR interval variability compared with control subjects (P <.001). Relative PR variability (PRPP) index, calculated as the ratio of normalized PR variability to cycle length variability, was significantly higher in coronary patients (P =.001) and did depend on the degree of coronary artery disease. We concluded that coronary artery disease is associated with decreased beat-to-beat fluctuations in AV conduction. Increased relative PR variability index suggests inhomogeneous AV conduction in stable coronary atherosclerosis.

Adult↗