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Biomedical subjects

I Ovsyshcher

Publications and source records attributed to I Ovsyshcher.

At least 19 recordsLinked to original sources
PubMed1999

A simple bedside test of 1-minute heart rate variability during deep breathing as a prognostic index after myocardial infarction.

BACKGROUND: We evaluate a simple, bedside test that measures 1-minute heart rate variability in deep breathing as a predictor of death after myocardial infarction. METHODS: Bedside heart rate variability was assessed in 185 consecutive patients 5.1 +/- 2.5 days after a first myocardial infarction. Patients were instructed to take 6 deep respirations in 1 minute while changes in heart rate were measured and calculated by an electrocardiographic recorder. An abnormal test result was defined as a difference of less than 10 beats/min between the shortest and longest heart rate interval. RESULTS: Heart rate variability <10 beats/min was found in 65 patients (35%) and was significantly lower (P <.05) in women, patients >60 years of age, patients with diabetes, patients with congestive heart failure, and patients taking angiotensin-converting enzyme inhibitors. Mean follow-up period was 16 months. Ten patients died during follow-up: 9 of cardiac causes and 1 of stroke. Nine of these 10 patients had heart rate variability <10 beats/min (P =.004). The sensitivity and specificity of this test for cardiovascular mortality is 90.0% and 68.0%, respectively. The negative predictive value is 99.2% and the relative risk is 16.6. Heart rate variability <10 beats/min remained a significant predictor of death after adjusting for clinical, demographic, and left ventricular function with an odds ratio of 1.38 (95% confidence interval, 1.13-1.63). CONCLUSIONS: This simple, brief bedside deep breathing test of heart rate variability in patients after myocardial infarction appears to be a good predictor for all-cause mortality and sudden death. It may be used as a clinical test for risk stratification after myocardial infarction.

Death, Sudden, Cardiac↗
PubMed1995

Evaluation of a new rate adaptive ventricular pacemaker controlled by double sensors.

UNLABELLED: The LEGEND-PLUS, a new rate adaptive pacemaker that combines activity and minute ventilation sensing for automatic rate adaptation was implanted in the right ventricle (VVIR) in 11 patients (mean age 62 +/- 9 years). Initial programming was performed using the Programmer Exercise Protocol (a 3-minute walk). This programming was evaluated by treadmill tests, up-stairs and down-stairs walking, and Holter recordings. RESULTS: Following the final programming of LEGEND-PLUS, the mean upper activity rate was 102 +/- 7 beats/min (range 90-120 beats/min), while the mean upper minute ventilation rate was 125 +/- 16 beats/min (range 100-150 beats/min). The mean rate responses during the exercise protocol and the final programming in minute ventilation and activity sensing modes were 5.4 +/- 2.3 (range 1-9), versus 4 +/- 2.4 (range 1-8; P < 0.01) and 7.6 +/- 1.1 (range 5-9), versus 7.5 +/- 0.8 (range 6-9; P = 0.8), respectively. In the combined sensing mode, the acceleration rate was identical to the activity rate response and the deceleration rate mimicked the minute ventilation. CONCLUSION: Dual sensor VVIR pacemakers have the potential to improve rate adaptation to exercise. The rate response to exercise in patients fitted with activity and minute ventilation sensors, VVIR pacemakers closely mimics the physiological rate response.

Adult↗
PubMed1993

Variability of cardiac output as determined by impedance cardiography in pacemaker patients.

Hemodynamic assessment of pacemaker patients is necessary for gauging responses to changes in programming or other conditions affecting circulation. Impedance cardiography permits noninvasive determinations of cardiac output at short intervals but data regarding variability of this method in patients with pacemakers is unavailable. Thirty-eight patients with pacemakers (24 with DDD and 14 with VVI devices) and 6 normal subjects were studied. Each patient was studied in the supine position and repeated impedance measurements were obtained. Fourteen patients were studied during sinus rhythm, 24 were studied during DDD pacing, and 32 patients were studied during VVI pacing. Variability was assessed by methods that analyzed both serial measurements and variability between 2 consecutive and nonconsecutive measurements. The mean indexes and coefficients of variation of 2 and serial measurements in sinus rhythm and DDD were 4%; in VVI it was 6%. The precision of impedance cardiography in all pacing modes, as demonstrated by analysis of variability, indicates that detected changes of stroke volume and cardiac output > 7% on serial (2 and more) measurements, performed by the same operator and during the same session, represent true hemodynamic alterations with 95% confidence. The precision of impedance cardiography demonstrated may be comparable or superior to other frequently used techniques, and the data obtained are valuable both investigationally and clinically.

Adult↗
PubMed1993

Measurements of cardiac output by impedance cardiography in pacemaker patients at rest: effects of various atrioventricular delays.

OBJECTIVES: The purpose of this study was to evaluate the ability of impedance cardiography to determine the change in cardiac output caused by modifications in the atrioventricular (AV) delay in DDD (dual-chamber) pacing mode while pacing the atrium and ventricle at different programmed rates. BACKGROUND: Impedance cardiography permits continuous noninvasive monitoring of hemodynamic variables on a beat to beat basis. METHODS: Eleven patients with a DDD pacemaker were evaluated by impedance cardiography. Stroke volume, cardiac output and total peripheral resistance were assessed in the supine rest position during both DDD and ventricular (VVI) pacing. Hemodynamic variables were measured during DDD pacing at rates ranging from 60 to 110 beats/min in 10-beats/min increments with programmed AV delay varying from 50 to 250 ms in 50-ms increments. When the pacemaker was reprogrammed to the VVI pacing mode, these measurements were repeated at the same pacing rates. RESULTS: Cardiac output measurements during programmed conditions were found to be highly reproducible. The mean coefficient of variation was 3% during DDD pacing; it was 6% in the VVI pacing mode. A large decrease in cardiac output (approximately 30%) was found when a pacemaker was reprogrammed from the DDD to the VVI pacing mode. At DDD pacing rates between 70 to 110 beats/min, the highest cardiac output occurred at an average AV delay of < 120 ms from atrial stimulus to ventricular stimulus. At an average AV delay of > or = 200 ms, the cardiac output in the DDD and VVI pacing modes was similar. CONCLUSIONS: 1) Impedance cardiography allows highly reproducible noninvasive assessments of cardiac output in pacemaker patients; 2) inappropriate programming of the AV interval in patients with atrial and ventricular pacing can decrease cardiac output significantly, and the extent of the decrease is similar to or less than that observed in ventricular pacing; 3) hemodynamic measurements obtained with impedance cardiography can facilitate optimal programming of pacemaker variables.

Cardiac Output↗
PubMed1993

Impedance cardiography for cardiac output estimation in pacemaker patients: review of the literature.

Impedance cardiography permits noninvasive beat-to-beat determination of cardiac output, the product of the amplitude of the first derivative of thoracic impedance signal (dZ/dt), the ventricular ejection time, and heart rate corrected by the distance between the measuring electrodes. Its use is based on: (1) the dZ/dt signal that originates from the upper thorax; (2) the ventricular ejection period measured by the dZ/dt curve that occurs between the opening and closing of the aortic valve; (3) the dZ/dt curve is similar in morphology and timing to the aortic flow curve measured by an electromagnetic flowmeter with a significant linear correlation (r = 0.9) between dZ/dt and peak aortic flow; (4) similarity of the linear correlation between stroke volume, determined by the flowmeter and the impedance signal; and (5) significant reduction of the dZ/dt signal by 90% follows simultaneous occlusion of the aorta and the pulmonary artery. The rapid systolic portion of the impedance signal occurs only when blood is ejected into the aorta and is independent of right ventricular ejection. Most studies comparing impedance cardiography results with standard cardiac output determination have shown a correlation of 0.7-0.9. While the accuracy of impedance cardiography remains controversial and can be affected by the inherent limitations of the technique and by low cardiac output, intracardiac shunts, and valvular regurgitation, the high reproducibility of the method is established and may be comparable or superior to other commonly used techniques. When accurate determination of cardiac output is crucial, impedance cardiography may be used in conjunction with a standard technique to establish a baseline reference, thereby permitting further analysis. If only the trend need be followed, the high reproducibility of impedance cardiography measurements allows small changes in cardiac output to be detected on a frequent and ongoing basis. The ease and precision of this technique warrants its more widespread use in the assessment of pacemaker patients. Further use of this promising technique will allow a better definition of its role in the assessment of a wide range of cardiac patients.

Cardiac Output↗
PubMed1993

[Thrombolysis for evolving myocardial infarction in a rural primary care clinic].

Early thrombolytic therapy gives maximum benefit in acute myocardial infarction. In remote rural areas with no mobile intensive care service there is a significant delay between onset of symptoms and administration of thrombolytic therapy which has a critical impact on revascularization. Thrombolytic therapy with streptokinase 1,500,000 U was given in a primary care rural clinic to 2 patients with evolving myocardial infarction 45-50 minutes from onset of symptoms. In both patients, who were transported to hospital after the therapy, there were clinical signs of reperfusion. There were no complications during treatment or transportation. We conclude that thrombolytic therapy given for evolving myocardial infarction in a rural primary care clinic is possible and safe.

Aged↗
PubMed1993

The prognostic importance of two easily obtainable noninvasive markers after intravenous thrombolytic therapy in acute myocardial infarction.

The predictability of left ventricular function, short- and long-term prognosis, assessed by means of two easily obtainable noninvasive markers, was prospectively studied in 110 consecutive patients undergoing thrombolytic therapy for acute myocardial infarction. Positive noninvasive markers were defined as follows: a) > 50% reduction in ST segment elevation within 120 min of initiating therapy, and b) early peak of creatine kinase (CK) activity < 12h after the start of thrombolysis. Seventy-five (68%) of the patients had two positive markers and are classified as the responder group. The nonresponder group consisted of 35 patients (32%) who had 0-1 positive markers. Left ventricular function was assessed 6-12 weeks after therapy by equilibrium radionuclide ventriculography. Left ventricular ejection fraction (LVEF) and survival rates at 1 month and 36 months were significantly higher in the responder group compared to the nonresponder group (54 +/- 12% vs. 43 +/- 11%, P < 0.05; 99% vs. 89%, P < 0.06; and 95% vs. 80%, P < 0.05 respectively). Thus, the combined analysis of two easily obtainable noninvasive markers can predict post-treatment preservation of left ventricular function and survival up to 36 months in patients with acute myocardial infarction undergoing thrombolytic therapy.

Adult↗
PubMed1992

Precision of impedance cardiography measurements of cardiac output in pacemaker patients.

Objective hemodynamic assessment of pacemaker patients is necessary for gauging responses to changes in programming or other conditions that affect the circulation. Impedance cardiography permits noninvasive, repetitive determinations of cardiac output at short intervals, but data regarding variability of this method in patients with pacemakers is unavailable. Thirty-eight patients with implanted pacemakers (24 DDD, 14 VVI) and six normal subjects were studied. A computerized impedance cardiograph was used to calculate cardiac output from the product of the first derivative of the thoracic impedance signal (dZ/dt), the ventricular ejection time, and heart rate. Each patient was studied while supine after a period of at least 15 minutes of rest and repeated impedance measurements (about ten) were performed. Fourteen patients were studied in sinus rhythm, 24 were studied during DDD pacing, and 32 patients were studied during VVI pacing. Cardiac and stroke indices were calculated 706 times on the basis of 11,296 accepted beats. Variability was assessed by methods that analyzed serial measurements and variability between two consecutive and nonconsecutive measurements. The mean indices and coefficients of variation of two measurements and of serial measurements in sinus rhythm and during DDD pacing were 4%; in VVI it was 6%. The precision of impedance cardiography in all pacing modes, as demonstrated by analysis of variability, indicates that detected changes of stroke volume and cardiac output > 7% on serial (two and more) measurements, performed by the same operator and during the same session, represent true hemodynamic alterations with 95% confidence.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Orthostatic responses in patients with DDD pacemakers: signs of autonomic dysfunction.

UNLABELLED: Responses to orthostasis may be altered in states associated with autonomic dysfunction. Computerized impedance cardiography, a noninvasive method for continuous assessment of stroke volume and mean blood pressure, was utilized to study the postural hemodynamic changes in eight normal and 27 patients with DDD pacemakers. Twenty patients with complete heart block (five with heart failure) were studied in the VDD mode and seven patients with sick sinus syndrome were assessed in DVI (four) or VDD (three). The results with pacemaker patients are significantly different from those observed in normal. Pacemaker patient responses to standing included: (1) a reduction in systolic, diastolic, and mean blood pressure; (2) an increase in heart rate in patients with intact sinus node function and no change in patients with sick sinus syndrome; and (3) stroke volume was unchanged in patients with sick sinus syndrome or heart failure and only modest reduction occurred in the remaining patients. CONCLUSIONS: (1) No reduction in stroke volume during upright posture occurs in DDD patients with sick sinus syndrome and this appears to be a compensatory reaction to an inadequate heart rate response to standing; (2) The hemodynamic response of DDD patients to the assumption of an upright posture is consistent with autonomic dysfunction; and (3) The primary cause for autonomic dysfunction in DDD patients may be the asynchronous ventricular depolarization caused by right ventricular pacing.

Aged↗
PubMed1992

First derivative of right ventricular pressure, dP/dt, as a sensor for a rate adaptive VVI pacemaker: initial experience.

Ten patients underwent implantation of a rate adaptive ventricular pacing system with a new pulse generator and lead. The unipolar lead has a steroid eluting tip and a pressure sensor. The first derivative of the signal from this sensor, dP/dt, is determined and the pacemaker rate is varied in response to changes in the right ventricular dP/dtMAX. During implantation, dP/dt values were in the range of 180-720 mm Hg/sec. The autothreshold for pacing at 2.5 V remained unchanged 1 month after implantation (0.065 +/- 0.045 msec, range 0.05-2.00 msec) and only slightly increased after 3 months (0.075 +/- 0.045 msec, range 0.05-2.00 msec). A significant correlation existed between the dP/dt measured during implantation and the right ventricular pressure measured by telemetry at follow-up visits (r = 0.93, P = 0.0001). Initial pacemaker programming was performed on the second day after implantation following a short walk and was adjusted subsequent to follow-up visits according to the patient's subjective assessment and in accordance with the results of exercise tests and Holter monitoring. Exercise and Holter tests did not significantly change initial programming. There was a significant correlation between right ventricular systolic pressure and the rate response setting (r = -0.66, P less than 0.05). During dP/dt pacing, all patients felt well, and eight of these reported an improvement compared to nonrate adaptive pacing. The heart rate response to effort and recovery was appropriate. It was concluded that: (1) right ventricular dP/dt is a suitable parameter for controlling the pacing rate; (2) appropriate programming of the dP/dt pacemaker results in a suitable heart rate response to exercise and recovery.

Aged↗
PubMed1992

Short- and long-term comparative study of anistreplase versus streptokinase in acute myocardial infarction.

Streptokinase is well established as an effective thrombolytic. Anistreplase, a new thrombolytic drug, is a complex of streptokinase and acylated human plasminogen that can be administered by intravenous bolus and activates plasminogen at the clot site. Although both streptokinase and anistreplase are effected in treating myocardial infarction (MI), they have different pharmacologic properties. This study was designed to identify short- and long-term differences in their clinical effectiveness, safety in use, and survival rates in patients with acute MI. One hundred ten successive patients under seventy years of age admitted within three hours after onset of sustained chest pain suggestive of acute MI were randomized to receive either 30 units of anistreplase intravenously over five minutes or intravenous injection of 750,000 units of streptokinase over thirty to sixty minutes. Reperfusion was achieved in 34 of the 52 (65%) patients treated with anistreplase and in 41 of the 58 (71%) patients treated with streptokinase (p = NS). The two drugs were equally effective in preserving left ventricular ejection fraction, which was found to be significantly better in patients with anterior wall MI who had achieved reperfusion than it was in those who did not (p less than 0.02). One-month, twelve-month, and thirty-six-month survival rates were high (96% to 88%) with no significant difference between the two treatment groups. The authors conclude that the two drugs are equally effective thrombolytic agents but that anistreplase has the advantage that it can be administered as a bolus injection.

Aged↗
PubMed1990

Electrocardiographic manifestations of combined hypercalcemia and hypermagnesemia.

Near drowning in the Dead Sea is a potentially lethal accident; the swallowing of the salty water causes acute combined hypercalcemia and hypermagnesemia, and this, rather than aspiration, is considered to be the main pathogenetic fator. The authors reviewed the electrocardiographic data of 37 patients who nearly drowned in the Dead Sea. Common findings in the acute phase included P wave changes, tendency for prolongation of P-R interval, prolongation of QRS complex, infra-His conduction disturbances, tendency for broadening and inversion of T wave, and the appearance of a prominent U wave. Three patients had potentially lethal ventricular tachyarrhythmias. The QaTc interval (beginning of QRS complex to apex of T wave, corrected for heart rate), the expected QaTc calculated from calcium blood level (QaTce), and their difference (DQaTc), were measured or calculated. The QaTc was found within normal limits and did not change during recovery from the Dead Sea water poisoning. The DQaTc correlated significantly with serum magnesium level (p less than 0.001). This correlation signifies that hypermagnesemia normalizes the QaTc interval, which is usually shortened by isolated hypercalcemia. Combined hypercalcemia and hypermagnesemia can be caused by swallowing excessively salty water. The potential cardiac complications require strict monitoring and electrocardiographic follow up study.

Arrhythmias, Cardiac↗
PubMed1990

Improved left ventricular function in myocardial infarction following intravenous thrombolytic therapy with acylated plasminogen activator.

Forty-six patients with acute myocardial infarction (MI) were treated within three hours of the onset of chest pain with an intravenous bolus (IV) of 30 units of anisolated plasminogen activator streptokinase complex (APSAC). Reperfusion was detected in 31 patients (67%) by clinical, electrocardiographic, and enzymatic criteria. The mean time elapsed between the onset of the chest pain to thrombolytic therapy was 114 +/- 53 minutes. Left ventricular ejection fraction (LVEF) was significantly better in patients with anterior and inferior myocardial infarction who had successful reperfusion, as compared with those who did not (48.8 +/- 13.0 vs 35.3 +/- 10.9, p less than 0.05 and 59.7 +/- 12.6 vs 47.9 +/- 15.3, p less than 0.05, respectively). The rate of reocclusion within three weeks was 22%. The overall one-year mortality was 4%. There were no serious adverse reactions following the thrombolytic treatment. Thus bolus IV injection of 30 units of APSAC is both safe and effective in preserving left ventricular function when given early in the course of acute myocardial infarction.

Adult↗
PubMed1989

[Long-term follow-up of prosthetic heart valves].

257 patients underwent single or double heart valve replacement between 1964-1986. In 141 (55%) after isolated mitral valve replacement, operative mortality was 14.8% and after 5, 10, 15 and 20 years, actuarial survival was 84%, 70%, 59% and 44%, respectively. In 70 who underwent isolated aortic valve replacement, operative mortality was 7.1% and after 5, 10, 15 and 20 years, actuarial survival was 85%, 85%, 72% and 72%. In 46 who underwent combined aortic and mitral replacement, operative mortality was 4.3% and after 5, 10 and 15 years, actuarial survival was 78%, 71% and 71%.

Actuarial Analysis↗
PubMed1989

Dead Sea water poisoning.

A unique chemical intoxication by Dead Sea water and its resultant physiological effects of combined severe hypercalcemia and hypermagnesemia are described. Of 48 adult patients, 16 had at least one severe clinical manifestation of either disturbed sensorium or a syndrome similar to adult respiratory distress syndrome. The patients had tachyarrhythmias (11 of 38, 29%), conduction disturbance (nine of 37, 24%), and a normal QTc interval in the presence of severe hypercalcemia. Combined respiratory and metabolic acidosis and concomitant extreme hypercalcemia and hypermagnesemia, reaching serum levels up to 28.8 and 33 mg/dL, respectively, were responsible for most of the clinical findings. The adult mortality was 19%. Four pediatric patients with variable degrees of intoxication survived. Discriminant function analysis determined that admission serum calcium concentration of more than 15.5 mg/dL was the best predictor of mortality. In patients with severe intoxication, supportive medical treatment, including forced diuresis, was disappointing. Early dialysis for severe cases merits further study.

Adult↗