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Biomedical subjects

H Kulbertus

Publications and source records attributed to H Kulbertus.

At least 19 recordsLinked to original sources
PubMed1992

Incidence, pathophysiology and prognosis of exercise-induced sustained ventricular tachycardia associated with healed myocardial infarction.

Of 150 consecutive patients with sustained monomorphic ventricular tachycardia (VT) (n = 116) or ventricular fibrillation (VF) (n = 34) late after acute myocardial infarction, 17 had reproduction of their sustained monomorphic VT during exercise testing. Data from these patients (group I) were compared with data from patients without exercise-induced VT (group II). No statistical difference was found between groups I and II with relation to age, sex, number of vessels with greater than 70% stenosis, left ventricular ejection fraction, number of previous myocardial infarctions, inducibility during programmed stimulation and total mortality during follow-up. In group I, only 1 patient (6%) developed ST depression during exercise compared with 47 patients (35%) in group II (p less than 0.01). After a 34-month mean follow-up, 6 patients in group I (35%) and 18 patients in group II (13%) died suddenly (p = 0.02). It is concluded that sustained monomorphic VT is reproduced during exercise in only 11% of patients with spontaneous late sustained monomorphic VT or VF. Electrocardiographic findings do not support ischemia as a triggering mechanism of exercise-induced sustained monomorphic VT. Patients with exercise-induced sustained monomorphic VT have a high incidence of sudden death.

Coronary Angiography↗
PubMed1992

Effect of spinal cord stimulation on regional myocardial perfusion assessed by positron emission tomography.

Spinal cord stimulation (SCS) can relieve symptoms in patients with severe angina pectoris refractory to conventional medical or surgical therapy. This symptomatic improvement may result from decreased myocardial ischemia. To test this hypothesis, positron emission tomography (PET) and potassium-38 as a flow tracer were used in 8 patients for the quantitative evaluation of regional myocardial perfusion at rest and after exercise, before and during SCS. Potassium uptake was evaluated as myocardial clearance (flow times net extraction) in ml/min/100 g. Tomographic segments were categorized as nonaffected and affected on the basis of the absence or presence of arterial stenosis on coronary angiography and on the basis of thallium scintigraphic data. In nonaffected segments, before SCS, regional myocardial clearance significantly increased from rest (28 +/- 4) to exercise (47 +/- 13 clearance units; p less than 0.004). A similar increase occurred after SCS. In affected segments, before SCS, regional myocardial clearance barely increased (p = 0.065) from rest (26 +/- 6) to exercise (33 less than or equal to 12). In comparison, after SCS, the resting regional myocardial clearance was slightly elevated (29 +/- 8) reflecting an increased double product, but did not increase (p = 0.192) with exercise (34 +/- 12). However, the magnitude and duration of ST-segment depression decreased during treatment with SCS. Anginal pain occurred in all patients during control exercise, but was attenuated in all but one with SCS. These results indicate that SCS improves exercise-induced angina and electrocardiographic signs of ischemia but this influence does not appear to be mediated by changes in regional myocardial perfusion.

Aged↗
PubMed1992

Usefulness and adequacy of sensor data storage and retrieval for rate response simulation.

The usefulness of sensor data storage for rate response simulation was evaluated using a new dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay 294-03 [Intermedics Inc.]). The pacemaker can store the sensor output during routine exercise and those values can be used to simulate rate profiles for other rate response settings. The predictive value of this feature was evaluated in three studies (mechanical, external pacemaker, and implanted pacemaker). In the first study, the pacemaker was submitted to three runs of eight different mechanical calibrated to-and-fro movements. In the second study, nine external pacemakers were strapped on healthy volunteers who performed three jogging tests. Finally, the predictive value of the simulation was studied in five implanted patients during three successive walking tests. In each study, the pacemaker was submitted three times to the same activity. The responsiveness was successively set to 5, 1, and 10, and the pacemaker outputs were continuously recorded on a Holter monitor. At the end of the first run, rate profile simulations for slopes 1 and 10 were performed; slope 5 rate response was simulated after the second run. A regression analysis was used to establish the correlation between predicted and achieved pacing rates for each study. The coefficients of correlation between predicted and measured pacing rates for the mechanical, external, and clinical studies were 0.999, 0.985, and 0.823, respectively. The corresponding slopes of regression lines were 1.005, 0.971, and 0.935. Calculated rate profile has a high predictive value and could be used to optimize rate responsive settings without serial exercise testings.

Acceleration↗
PubMed1992

Clinical interest of a sensor driven algorithm limiting ventricular pacing rate during supraventricular tachycardia in dual chamber pacing.

UNLABELLED: A sensor driven algorithm limiting ventricular pacing rate during supraventricular tachycardia (SVT) is included in a dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay, 294-03, Intermedics Inc.). According to the intensity of concomitant exercise, the ventricular pacing rate is limited either to the programmed maximum pacing rate (MPR) or to an interim lower limit, called "conditional ventricular tracking limit" (CVTL). The MPR prevails over the CVTL when the sensor calculated pacing rate exceeds the minimal rate by more than 20 beats/min. The purpose of the study is to determine the clinical safety and efficacy of this algorithm in patients with intermittent SVT. METHOD: A Relay was implanted in four patients with a bradycardia/tachycardia syndrome and in four patients with complete atrioventricular block (CAVB). All had episodes of paroxysmal atrial tachycardia. The units were programmed in DDDR: rate responsive parameters were adjusted by simulating the rate response during three levels of exercise to let the MPR override the CVTL only during strenuous exercise. Holter monitors and exercise testings were performed at 3-month follow-up. RESULTS: In seven patients, Holter recordings showed supraventricular arrhythmias at rest with a ventricular pacing rate limited to the CVTL. Appropriate rate increases during exercise testings were also demonstrated. Three devices had to be reprogrammed in DDIR (one patient suffering from nearly permanent atrial flutter and two patients not tolerating the CVTL pacing rate at rest). CONCLUSION: The CVTL algorithm is effective in protecting against high ventricular pacing rates during supraventricular arrhythmias. It allows the selection of the DDDR mode even with a high MPR in patients with intermittent SVT.

Acceleration↗
PubMed1992

In vitro evaluation of a sensor sensitive to acceleration forces included in a new rate modulated pacemaker.

UNLABELLED: The characteristics of the sensor and rate adaptive algorithm included in a new dual chamber rate responsive pacemaker (Relay 294-03, Intermedics, Inc.) were studied by submitting the device to calibrated to-and-fro movements of specific frequencies and peak accelerations by means of a mechanical arm connected to a speed adapter. Atrial pacing rate was continuously recorded on a Holter monitor. The influences of the frequency, the magnitude, and the axis of the acceleration forces as well as the reproducibility of the rate response were evaluated. RESULTS: (1) The sensor was sensitive to frequencies ranging from 0.5 to 7 Hz with a peak sensitivity at 3 Hz; (2) the pacing rate was not affected during movements at frequencies > 6 Hz, commonly presented as nonactivity related signals (car, bus transportation, drilling....); (3) the pacing rate increased as a function of the acceleration magnitude up to 0.5 G (0.3 G for 3 Hz), then remained constant. This level of acceleration usually corresponds to high degrees of activity; (4) rate response was maximum when acceleration was directed in the anteroposterior direction; (5) reproducibility of the rate response was excellent (R2: 0.999; slope of the regression line: 0.999). CONCLUSION: Relay 294-03 is a low frequency signal sensing rate modulated pacemaker using an accelerometer sensitive to motion, mainly in the anteroposterior direction.

Acceleration↗
PubMed1990

Imaging of myocardial metabolism by positron emission tomography.

Tracer techniques have provided new insight in cardiology by allowing noninvasive studies of myocardial perfusion, function, metabolism, and, more recently, ligand-receptor interaction. Positron emission tomography allows accurate quantification and the use of natural substrates labelled with 11C, 13N, or 15O. Myocardial metabolism is complex and utilizes a number of substrates, primarily fatty acids. Fatty acids utilization can be studied with 11C palmitate, while 11C acetate more selectively traces TCA cycle activity and reflects myocardial oxygen utilization. Glucose uptake can be traced using 18F deoxyglucose, a glucose analog that is a substrate for hexokinase but is not further metabolized. Flow and oxidative glucose metabolism are usually coupled, and thereby the uptake of FDG and perfusion tracers are usually similar. In myocardial ischemia, however, glucose utilization can persist due to anaerobic glycolysis, and its uptake is frequently enhanced. Clinical applications of the use of metabolic studies in patients with ischemic heart disease are presented.

Amino Acids↗
PubMed1990

99mTc-MIBI (RP-30) to define the extent of myocardial ischemia and evaluate ventricular function.

99mTc-MIBI, a new myocardial perfusion agent, is a technetium labeled isonitrile derivative. We have taken advantage of the physical characteristics of 99mTc to combine at rest, post infarction, ventricular function studies with analysis of perfusion. We have studied at rest and at stress, 22 patients with coronary artery disease selected on the basis of an abnormal coronary angiogram or on the basis of a positive exercise ECG stress test for symptomatic angina. We have also studied, at rest only, 20 patients with a previous myocardial infarction. A comparative thallium planar scintigraphy was obtained for all patients. The sensitivity of 99mTc-MIBI scintigraphy for detecting individual vessel lesions at stress was 88% as compared with 83% for 201Tl. Sensitivity was higher in patients with previous myocardial infarction (93% for the 2 isotopes) than in patients without (85% for 99mTc-MIBI versus 81% for 201Tl). Segmental myocardial correspondence between 99mTc-MIBI and 201Tl was very close (92%). The overall sensitivity for the detection of acute myocardial infarction reached respectively 91% for 99mTc MIBI and 87% for 201Tl. The specificity in the regions corresponding to arteries not involved was excellent for both tracers as we did not observe any false positive result. This is important information but it does not correspond to the specificity to detect coronary artery disease in the overall patient population. The correlation between first pass left ventricular ejection fraction obtained with 99mTc-MIBI and equilibrium left ventricular ejection fraction obtained with 99mTc red cells was excellent (r = 0.96). It was not as good but was still satisfactory for the right ventricle (r = 0.75).(ABSTRACT TRUNCATED AT 250 WORDS)

Contrast Media↗
PubMed1990

Clinical experience with a new catheter for His bundle ablation.

Eleven patients aged 33-66 years were referred for treatment of refractory supraventricular arrhythmias. Each patient had failed to respond to medical treatment. One patient had a paroxysmal atrial flutter with a rapid ventricular response. Six patients had a chronic atrial fibrillation. Two others had a supraventricular tachycardia due to reentry in the atrioventricular (AV) node, and two patients suffered from circus movement tachycardia using a concealed left free wall accessory pathway. A specially built United States Catheter and Instruments (USCI) women Dacron polyurethane electrode catheter (bipolar 8F with an internal lumen, 90 A, 5,000 V, 5.5 omega) was positioned in the His bundle area to record unipolar large atrial and His signals. When the maximal ratio low right atrium/His spike was recorded, the pole was connected to the output of a standard defibrillator. A shock of 200-250 J was delivered through this pole. Ten patients developed complete AV block (CAVB) immediately. After 72 hours, these patients were implanted with a rate-responsive pacemaker. The procedure was without side effects. Nine patients remain in CAVB after 3-17 months; in one case AV conduction resumed but the patient is free of arrhythmia. Another patient needed a second catheter ablation after 1 month.

Adult↗
PubMed1989

[A european multicenter and randomized study of APSAC versus streptokinase in myocardial infarction].

In a multicentre randomized open study conducted on two parallel groups the effectiveness of APSAC was compared with that of streptokinase (SK) in 116 cases of myocardial infarction treated during the first 2.75 hours. APSAC (30 IU) was administered by intravenous bolus injection over 2 to 5 minutes, and SK (1.5 million IU) by intravenous infusion over 60 minutes. The patency of the coronary artery responsible for myocardial infarction was evaluated by coronary arteriography performed 1.74 h on average after the beginning of treatment; it was 70 p. 100 in the APSAC group and 51 p. 100 in the SK group (p less than 0.05). The fall in plasma fibrinogen was similar in both groups (mean minimum level; 0.2 g/l). Haemorrhages occurred in 9/58 patients treated with APSAC (15.5 p. 100) and in 13/58 patients treated with SK (22.4 p. 100); these haemorrhages took place during the first 24 hours in 4 patients of the APSAC group and in 10 patients of the SK group. Five patients died: 2 in the APSAC group and 3 in the SK group. In a subgroup of 38 patients who underwent 3 control coronary arteriographies (at 90 min, 24 hours and 3 weeks), the patency rates were 63 p. 100, 82 p. 100 and 93 p. 100 respectively with APSAC and 44 p. 100, 86 p. 100 and 92 p. 100 respectively with SK (NS). No coronary reocclusion occurred in the APSAC group, as against 3 (1 early, 2 delayed) in the SK group. It is concluded that APSAC seems to be more effective than intravenous streptokinase; it is easier to administer (bolus injection) and does not carry a higher risk of haemorrhage.

Anistreplase↗
PubMed1989

Antegrade conduction over a concealed accessory pathway after His bundle catheter ablation.

The existence of unidirectional retrograde preexcitation or concealed bypass fibers and their role in paroxysmal supraventricular tachycardia have been known for a long time. However, the exact anatomic and physiological nature of this retrograde limb remains unclear. We report here on a patient who had a concealed accessory pathway (AP) with circus movement tachycardia. After His bundle catheter ablation the AP had the property to conduct in the antegrade direction. The absence of antegrade conduction over the AP before ablation is likely due to its decremental properties of conduction and to repetitive retrograde concealed conduction from the normal pathway.

Adult↗