Biomedical subjects

B Gersak

Publications and source records attributed to B Gersak.

At least 19 recordsLinked to original sources

PubMed2003

Beat-to-beat QT interval variability before and after cardiac surgery.

Non-uniform recovery of excitability may be essential in triggering malignant ventricular tachycardia after cardiac surgery. Thirty-five channels ECG was recorded for 6 min in 27 patients before and after heart surgery and in 20 control subjects. Off-line analysis was performed. RR interval duration, RR SD, QT SD and power spectra of RR variability were computed from 256 s stable RR and QT interval series. When compared to controls, patients had decreased RR SD and increased QT SD before surgery (p<0.002 and p<0.0005, respectively); RR SD further decreased and QT SD increased after the surgery (p<0.0001 and p<0.0002, respectively). Increase of QT variability and decrease of RR variability after cardiac surgery may reflect disrupted electrophysiological stability of the myocardium and thus electrophysiological substrate for triggering malignant arrhythmia.

Aged↗

PubMed2001

Imaging of power spectral heart rate variability regarding subject position.

Heart rate variability (HRV) and its assessment using power spectral analysis revealed a possibility to quantify the characteristics of autonomic nervous system, related cardiovascular status and sympathovagal interaction. This study was designed to assess vagal tone in supine and right recumbent position in normal healthy subjects as many maneuvers that potentially increase vagal tone have been sought both in normal subjects and in patients with heart disease. Seven subjects, four male and three female, aged 20-27 years were enrolled in the study. To evaluate the time-dependent stability of short term ECG recordings, every subject participated in six ECG recording sessions (three successive morning and three successive afternoon measurements). Heart rate power spectra were obtained by off-line Fast Fourier Transform analysis. The frequency domain measures, namely very low frequency power (VLF), low frequency power (LF), high frequency power (HF) and total power were determined, and their normalized correlates used in the comparison between supine and right recumbent position. Normalized high frequency (nHF) indicated cardiac vagal activity, normalized low frequency power indexed sympathetic modulated activity, low frequency power/high frequency power ratio (LF/HF) represented sympathovagal balance. The results showed remarkable variation among successive day measurements as well as among study subjects. However, several types of response to adopting right recumbent position could be identified. In the first, in right recumbent position the values of nHF, indicator of vagal activity did not differ appreciably from the values measured in supine position. Secondly, there was a tendency towards higher nHF values and lower LF/HF power ratio in supine position. We were not able to notice any appreciable difference among morning and afternoon short-term measurements. Finally, our results do not suggest higher vagal modulation when lying in right recumbent position.

Adult↗

PubMed2001

Visualization of computer simulated heart temperature during topical cooling.

A local hypothermia is often used during cardiac operations to slow down the tissue metabolism. The heart is cooled down with cold cardioplegic solution. Sometimes even the topical cooling with or without ice slush is used. Different heart models have been used earlier to simulate heart temperature distribution, but the resolution of the model has always been limited by the speed of the computer. We used the computer heart model derived from Visible Human Dataset with the spatial resolution of 1 mm. In this article, the step-by-step generation of 3D computer heart model is described. The heat transfer was modeled by a diffusion equation that was discretised in space and time and solved by a parallel algorithm. Finally, the cooling of heart during an operation, with and without topical ice slush, was simulated on a cluster of 9 PC-based computers, which assured sufficient computing power. The simulated results are presented as images of cross sections in different planes with temperatures shown by different colors.

Body Temperature↗

PubMed2000

Transtelephonic transmission of electrocardiograms in Slovenia.

The transtelephonic transmission of electrocardiograms (ECGs) was introduced in Slovenia in 1996 and has been used regularly since September 1997 by health institutions and patients with cardiovascular diseases. Portable 12-channel ECG equipment weighing less than 200 g is generally used. The diagnostic centre is located in the intensive-care unit at the University Medical Centre Ljubljana. In the first 12 months of regular operation we received 463 calls, 213 of which were diagnostic. The most common reasons for calling were: ischaemic chest pain, atypical chest pain, palpitations and dyspnoea. The most common diagnoses made on the basis of history and the ECG were: acute myocardial infarction, angina pectoris, paroxysmal tachycardias and atypical chest pain. In 40% of cases the cardiologist's advice sufficed; 38% of patients were referred to the emergency room, 29% immediately and 9% only if a suggested therapy did not prove successful; and in 21% of cases new medication or a change of dosage of current medication was suggested. Transtelephonic ECG transmission enables direct communication between general practitioner or patient and cardiologist. With its use, time from onset of symptoms to initiation of treatment is shortened, which reduces disability and mortality due to cardiovascular diseases and improves cost-benefit.

Cardiovascular Diseases↗

PubMed2000

Spatial resolution of epicardial pace mapping using body surface potentials.

Body surface potential maps (BSPMs) recorded during pace mapping provide an important non-invasive means for identifying local cardiac events; recent clinical studies demonstrated that endocardial pacing sites can be resolved within less than 10 mm. We sought to determine whether similar spatial resolution could be achieved during epicardial pacing. Four patients who were undergoing either heart valve replacement (one), aortocoronary bypass graft (one), or both (two) were studied. In each patient, a pair of epicardial electrodes was placed intraoperatively at the middle aspect of the right ventricular free wall. The distance between the neighbouring electrodes was 10 mm. Five days after the surgery, ECGs were acquired from 35 leads during pacing from each epicardial electrode. We determined the distributions of QRS integrals (the net area under the ECG signal) and compared integrals corresponding to pacing from each of the adjacent electrodes using statistical indices. Student's t-test was applied to these indices and in all the patients revealed that differences in distributions of QRS integral maps were statistically significant (p < 0.01). Results of our study indicate that the non-invasive acquisition of body surface ECGs could resolve epicardial breakthrough sites within 10 mm, which may be useful in facilitating therapeutic ablations in patients with ventricular tachycardias.

Aged↗

PubMed2000

Measurement of porcine heart temperatures.

During cardiac surgery local hypothermia of the heart is used to slow down cellular metabolism. It has been shown by computer simulation that heart muscle is not uniformly cooled to the desired temperatures. The aim of our work was to find out a way for measuring the temperatures of the ventricular wall and the septum with +/-0.1 degrees C accuracy. The measurement protocol should be applicable during operations on the human heart, during which disturbing factors should be minimized. We have tested the protocol and the equipment on porcine hearts. Two types of probes were tested, the contact-probe, which can be attached to the heart-wall surface, and the needle-probe, which can be inserted into the heart tissue. Before experiments the probes were calibrated and their heat transfer characteristics determined. We conclude that the probes and the protocol are suitable for studying the effects of cardioplegia, and for checking the results previously obtained by computer simulation.

Animals↗

PubMed2000

Mitral valve repair or replacement on the beating heart.

BACKGROUND: Beating heart (off-pump) coronary artery bypass grafting (CABG) techniques have led us to consider the possibility of performing mitral valve repairs and replacements (with or without CABG) on the beating heart. METHODS: If CABG had to be performed in addition to the valve procedure, CABG was done first on the beating heart without cardiopulmonary bypass, if possible. For the valve procedure, the aorta was cross-clamped and the beating-heart status was maintained throughout the whole procedure with continuous, warm, oxygenated blood coronary-sinus perfusion. RESULTS: We used this technique in 23 patients with extremely low ejection fractions, 78% of whom were in New York Heart Association (NYHA) class 4 and 17% of whom were in New York Heart Association (NYHA) class 3. The procedures were: mitral-tricuspid (11 patients), mitral-aortic (7 patients), mitral-tricuspid CABG (1 patient), and mitral-aortic CABG (4 patients). The total early mortality was 13% (3 of 23 patients). Two were in-hospital deaths. One patient with triple-vessel disease and acute mitral insufficiency (AMI) on intra aortic balloon pump had been operated on six days after AMI. The cause of death was systemic meticillin resistant staphylococcus aureus infection. (Eight days prior to our operation, arthrodesis of the talocrural joint was performed by an orthopedic surgeon.) The other death was a female patient who was operated on after previous multiple cerebrovascular infarctions (CVIs) (cause of the death was CVI). In addition, one patient died one month after the operation because of prosthetic valve endocarditis on aortic and mitral valves (silver-coated silzone aortic and mitral valves were implanted because of chronic latent asymptomatic tibial osteitis). None of these deaths were cardiac related. CONCLUSIONS: The main advantages of beating heart surgery are: 1) the perfused myocardial muscle, 2) the heart not doing any work, 3) no reperfusion injury, 4) the possibility for ablation of atrial fibrillation on the beating heart, and 5) testing of the mitral valve repair is done in real physiologic conditions in the state of left ventricle beating tonus. The procedure could be the procedure of choice for the valve operation or combined operations in high-risk patients with low ejection fractions.

Adult↗

PubMed1999

Results of treatment of 17 patients with heart tumour.

BACKGROUND: Between 1989 and 1997, 17 patients underwent surgery for excision of primary cardiac tumour at the Department for Cardiovascular Surgery in Ljubljana. PATIENTS AND METHODS: There were 13 female (76.5%) and four male (23.5%) patients with an average age of 49+/-14 years (mean+/-SD). The study was retrospective. Special attention was paid to clinical presentation, method of diagnosis, elapsed time between the confirmed diagnosis and excision of the tumour, operatively determined location of tumour and post-operative course-diuresis in first 48 h, levels of CK and CK-MB, on first and on second day after operation and time of hospitalization. RESULTS: Thirteen patients (76.5%) had cardiac symptoms at the time of presentation (dyspnoea, syncope, vertigo, palpitations) and four (23. 5%) had embolic complications. In all the patients diagnosis was made by echocardiography. Average elapsed time between the confirmed diagnosis and the operation was 26+/-40 (mean+/-SD) days. Histological examination revealed myxoma in 15 patients (88.2%), one patient had lipoma and one malignant haemangiosarcoma. The most common location of tumour was in the left atrium (12 patients; 70. 6%). Post-operative complications occurred in four patients (23.5%); 76.5% of patients had diuresis in the range between 0.8 and 2.0 ml/h/kg; there was no post-operative oligouric renal failure. Average levels of both CK and CK-MB were statistically significantly lower on the second day after operation, there was no case of peri-operative myocardial infarction and post-operative death did not occur. One patient with multiple myxoma had two recurrences. CONCLUSIONS: Symptoms in patients with heart tumours, especially at the beginning of illness, are often uncharacteristic. Due to the non-specific presentation of cardiac tumours, a high index of suspicion is needed. The diagnostic method of choice is echocardiography. Operative removal of tumour is a safe procedure and recurrences in patients with benign tumours are rare.

Adult↗

PubMed1999

Transtelephonic ECG in Slovenia.

Transtelephonic ECG has been introduced in Slovenia in 1996. It has been operating on a regular basis since September 1997. Users of the system are health institutions and patients with CV diseases. They use portable 12-channel ECG weighing less then 200 grams. Diagnostic center is located in medical ICU in Clinical Center Ljubljana. In the first 20 months of regular operation we have received 852 calls, 450 of them being diagnostic. The most common reasons for calling were: ischaemic chest pain, atypical chest pain, palpitations and dyspnoea. Most common diagnoses made on the basis of history and ECG were: AMI, angina pectoris, paroxysmal tachycardias and atypical chest pain. In 186 cases the cardiologist's advice sufficed, 171 patients were referred to the ER, 142 immediately and 29 only if suggested therapy hadn't been successful. To 82 patients new medication or changed dosage of previous medication was suggested. With the intent to evaluate accuracy of the diagnoses made on the basis of history and transtelephonic ECG evaluation we followed up the patients who were sent to ER in Ljubljana upon our cardiologists' advice. On the basis of preliminary results we can conclude that TTE is as diagnostic as the conventional ECG and its' use shortens time from onset of symptoms to initiation of treatment, it lowers disability and mortality due to CV diseases and improves cost benefit.

Arrhythmias, Cardiac↗

PubMed1999

The telemedicine and second medical opinion.

Telemedicine is declared as delivery of care to patients anywhere in the world by combining communications technology, with medical expertise. The well established applications of telemedicine are in the field of teleradiology, pathology, cardiology. In some cases video-conferencing (VC) may be applied. Second medical opinion is an important additional viewpoint on the patient diagnosis and treatment. The established network of consultant hospitals and worldwide Second opinion centers enable a fast (24-72 hours response) second medical opinion consultation service with the telemedicine application. The consultant hospitals at present time are: UCSF--San Franscisco, Stanford Medical Center, Bowman Gray School of Medicine, The Brigham Radiology Foundation, Emory University Hospital, University of Pennsylvania Medical Center. The second opinion centers are located worldwide, just to mention some of them: London, Budapest, Ljubljana, Tel Aviv, Bombay, Athens, Milano, Seoul.

Humans↗

PubMed1998

Computer simulation and spatial modelling in heart surgery.

In this work, three dimensional modelling and computer simulation of heat transfer on generally-shaped nonhomogeneous bodies is proposed and described. The complexity of the calculation is estimated and the potential use of high performance parallel computers is discussed. The method is focused on applications in medicine. As an example, a numerical algorithm for the parallel computer simulation of heart cooling procedures during surgery is presented. On the basis of simulated results, two different methods of cooling are compared.

Algorithms↗

PubMed1998

Loss of endothelium mediated vascular relaxation as a response to various clamping pressure. Part I. A pharmacological study.

BACKGROUND: The contraction/relaxation response of thoracic aortal rings clamped with two clamping pressures to KCl, noradrenaline and carbachol was studied. METHODS: Clamp A had the tip pressure PA = 0.60 N/mm2 and clamp B PB = 5.16 N/mm2. In fifteen Wistar albino rats, weighing 328 +/- 19 g (mean +/- SD) the thoracic aorta was occluded for 15 minutes and then three vascular rings (2 mm wide) were excised. The proximal unclamped ring served as a control. From distal rings the diameter of the aorta was calculated from their circumference 1.61 +/- 0.01 mm (n = 15, dmin = 1.51 mm, dmax = 1.70 mm). The rings were challenged with cumulative additions of KCl (10-80 mmol/l) to measure the contraction. Then cumulative relaxation to carbachol (0.01-100 mumol/l) as a response to noradrenaline precontraction (0.1 mumol/l) was determined. RESULTS: A significant loss (p < 0.05) of vascular relaxation in all clamped rings (clamped with PA and PB clamping pressures) was seen. No significant differences (p > 0.05) were observed for contraction between clamped and control rings clamped with clamp A, however the rings clamped with clamp B showed a significant reduction in contraction (p < 0.05). No significant differences were seen from control rings between groups A and B (p > 0.05), or from clamped rings between groups A and B (p > 0.05) for both the contraction and relaxation part of experiments. CONCLUSIONS: Endothelial vascular layers are much more susceptible to pressure injuries than was previously believed.

Animals↗

PubMed1998

Loss of endothelium mediated vascular relaxation as a response to various clamping pressures. Part II. Direct measurements of clamping pressures and scanning electron microscope study.

BACKGROUND: We used novel equipment for measuring the direct tip pressure (P) of a clamp arm on the vessel wall and studied the relationship between endothelial injuries and various clamping pressures. METHODS: A strain gauge was applied to the surgical clamp arm and connected via amplifier to a 12-bit analogue-digital converter on a PC--MSDOS computer. In the on-line in vivo measurements on rat thoracic aorta a momentary peak clamping pressure (MPCP) as well as the lower stationary clamping pressure (SCP) was defined. Clamping forces of two clamps commonly used in cardiovascular microsurgery were tested in the experiment on rat thoracic aortas: clamp A had the tip pressure p = 0.60 N/mm2 and clamp B p = 5.16 N/mm2. After 15 minutes of occlusion, the thoracic aorta was excised and scanning electron microscopy studies for aortas clamped with clamp A and clamp B were performed. RESULTS: Great endothelial lacerations with complete disruption of the endothelial layer in the rings clamped with the clamp B were seen, but no disruption in rings clamped with clamp A. CONCLUSIONS: The clamping vessel wall injuries, particularly in endothelial layers, depend on the momentary peak clamping pressure as well on the lower stationary clamping pressure.

Animals↗

PubMed1997

Direct measurement of clamping forces in cardiovascular surgery.

Equipment for measuring the direct tip force of a clamp arm on the vessel wall is designed as an adjustable surgical clamp with strain gauges applied and connected via an amplifier to a computer-based data acquisition system. A mechanical model that incorporates the resistance of tissue against momentary deformations is developed to analyse and justify measured results. In in vivo experiments on rat thoracic aorta, the minimum occlusion force, stationary clamping force and the momentary peak clamping force are measured and observed as an important cause of damages in the endothelial layer of vascular walls.

Anastomosis, Surgical↗

PubMed1997

[Successful surgical revascularization after 18 hour ischemia below the knee due to complete avulsion of the popliteal artery].

We report the case of a 33-year-old man after knee luxation and disruption of a popliteal artery, which was missed after repositioning at the first clinic. Eighteen hours later complete discontinuity of the popliteal artery was confirmed by arteriography and an immediate reversed, end-to-end auto-venous graft was interposed under general anesthesia with anterior and posterior fasciotomy prior to blood flow restoration. Forced diuresis with a diuretic mixture and balanced fluid intake were used, and the patient was discharged from the intensive care unit on the 10th postoperative day in good condition with normal diuresis.

Acute Kidney Injury↗

PubMed1996

Cor triatriatum sinistrum, aortic coarctation and bicuspid aortic stenosis in an adult.

Cardiac anomalies are usually diagnosed early in life, which is particularly true for their various combinations. The diagnosis in adulthood is rare. Here we report the case of a young man with an aortic coarctation corrected at the age of 16, however the associated stenotic bicuspid aortic valve and cor triatriatum sinistrum were corrected after Streptococcus viridans endocarditis 7 years later.

Abnormalities, Multiple↗

PubMed1996

Loss of endothelium-mediated vascular relaxation as a response to various clamping pressures.

The contraction/relaxation responses of thoracic aortal rings clamped with two clamping pressures to potassium chloride (KC1), noradrenaline and carbachol were studied using a scanning electron microscope (SEM) to ascertain endothelial lacerations. Clamp A had the tip pressure PA = 0.60 N/mm2 and clamp B PB = 5.16 N/mm2. In 15 Wistar albino rats, weighing 328 +/- 19 g (mean +/- SD), the thoracic aorta was occluded for 15 min and then three vascular rings (2 mm wide) were excised. The proximal unclamped ring served as a control. The aorta diameter was calculated from the circumference of distal rings 1.61 +/- 0.01 mm (n = 15, dmin = 1.51 mm, dmax = 1.70 mm). The rings were challenged with cumulative additions of KC1 (10-80 mmol/l) to measure the contraction. Then cumulative relaxation on the administration of carbachol (0.01-100 mumol/l) as a response to noradrenaline precontraction (0.1 mumol/l) was determined. A significant loss (P < 0.05) of vascular relaxation in all clamped rings (clamped with PA and PB clamping pressures) was seen. No significant differences (P > 0.05) were observed for contraction between clamped and control rings clamped with clamp A, however the rings clamped with clamp B showed significantly reduction of contraction (P < 0.05). No significant differences were seen from control rings between groups A and B (P > 0.05), as well as from clamped rings between groups A and B (P > 0.05) for both the contraction and relaxation parts of the experiments. With SEM, great endothelial lacerations with complete disruption of the endothelial layer in the rings clamped with the clamp B were seen, but no disruption in rings clamped with clamp A. Therefore endothelial vascular layers are much more susceptible to pressure injuries than was previously believed. The clamped vessel wall injuries, particularly in endothelial layers, depend on the momentary peak clamping pressure (MPCP) as well as on the lower stationary clamping pressure (SCP).

Adrenergic alpha-Agonists↗

PubMed1995

Successful surgical removal of partially expanded Palmaz stent from external iliac artery.

Insertion of intravascular stents into various arteries including coronary arteries has become an integral part of vascular interventions, particularly in the treatment of aortoiliac arteriosclerotic disease. The incidence of vascular complications remains relatively high despite the better stent design and inserting techniques. We report a case where successful removal of partially expanded Palmaz stent from external iliac artery was needed due to a rare complication: a balloon catheter burst resulting in an insufficient stent expansion in an improper position.

Aged↗