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Biomedical subjects

M Mirowski

Publications and source records attributed to M Mirowski.

30 records · Page 2Linked to original sources
PubMed1987

Pathologic findings related to the lead system and repeated defibrillations in patients with the automatic implantable cardioverter-defibrillator.

The purpose of the present study was to examine at autopsy the effect of multiple defibrillations on the myocardium and the pathologic consequences of short- and long-term placement of the intravascular and interpericardial leads of the automatic implantable cardioverter-defibrillator. Twenty-five patients were examined at autopsy; 8 of them underwent lead implantation only and 17 received both leads and the automatic implantable cardioverter-defibrillator. Twelve patients (48%) died of ventricular tachycardia or ventricular fibrillation; seven (28%) died of other causes. Acute pericarditis occurred in all patients, resulting in a localized, progressive fibrosis around the apical patch lead without giving rise to pericardial restriction. Thrombus formation was associated with the superior vena cava spring electrode in four patients (17%) and the right ventricular rate-sensing electrode in one patient (4%). Asymptomatic pulmonary emboli occurred in two patients (8%). In one patient who underwent defibrillation 59 times, superior vena cava changes consisted of vein wall destruction, fibrosis and thrombus formation. Pathologic changes under the apical patch related to defibrillation were observed in seven patients; two of these had fewer than 5 defibrillations, one had 8 defibrillations and four had 21 to 74 defibrillations. These changes consisted of contraction band necrosis in four patients, vacuolar cytoplasmic clearing and loss of myocytes confined to the myocardium under the patch electrode in five patients who had multiple defibrillations. The observed pathologic changes were estimated to affect less than 2% of the total myocardial mass. Thus, the automatic implantable cardioverter-defibrillator lead system and multiple defibrillations result in localized myocardial injury confined to the tissue under the patch electrode.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Treatment of malignant ventricular arrhythmias with endocardial resection and implantation of the automatic cardioverter-defibrillator.

Although ventricular resection guided by endocardial mapping has been a successful treatment for drug-refractory ventricular arrhythmias, 20 to 30 percent of patients still have postoperative sustained ventricular tachycardia or sudden death. To improve the outcome of the procedure, we implanted an automatic cardioverter-defibrillator in conjunction with endocardial resection in 28 patients, all of whom had had previous myocardial infarctions and between one and five cardiac arrests. There were three perioperative deaths. During follow-up of 8 to 51 months (mean, 25), 4 of the 25 survivors had recurrences of hypotensive ventricular tachycardia, which in all instances were automatically terminated by the implanted device. One patient, whose automatic cardioverter-defibrillator was not functional, died suddenly. We conclude that patients undergoing mapping-directed endocardial resection can be provided with additional protection against recurrent ventricular tachyarrhythmias or sudden death by implantation of an automatic cardioverter-defibrillator.

Adult↗
PubMed1986

[Implantable defibrillators. Clinical experience].

The clinical experience with the Automatic Implantable Cardioverter-Defibrillator (AICD) now extends to over 800 patients suffering from malignant ventricular arrhythmias, most of them survivors of sudden cardiac death. This device monitors cardiac rhythm for long periods of time, identifies ventricular fibrillation and life-threatening ventricular tachycardias, and then restores normal heart action with effective electrical discharges. The AICD practically eliminates the need for trained personnel and the time constraints associated with conventional out-of-hospital resuscitation, significantly decreasing the arrhythmic and total mortality rates of the implantees. Through August, 1985, 130 consecutive patients underwent implantation of the AICD at The Johns Hopkins Hospital in Baltimore; the one-year mortality due to arrhythmias was 1.7%. These results are similar to those reported by other centers. Thus, the growing clinical experience with the automatic implantable cardioverter-defibrillator has demonstrated a marked reduction of the mortality rate of the implantees.

Adolescent↗
PubMed1985

The automatic implantable cardioverter-defibrillator: an overview.

The automatic implantable cardioverter-defibrillator continuously monitors the heart, identifies malignant ventricular tachyarrhythmias and then delivers electrical countershock to restore normal rhythm. There are two defibrillating electrodes which are also used for waveform analysis; one is located in the superior vena cava and the other is placed over the cardiac apex. A third bipolar right ventricular electrode is used for rate counting and R wave synchronization. When ventricular fibrillation occurs, a 25 J pulse is delivered; when ventricular tachycardia faster than the preset rate is detected, the discharge is R wave-synchronized. The clinical evaluation study of this therapeutic method began in February 1980 in patients with recurrent refractory life-threatening ventricular tachyarrhythmias. So far, the device has been implanted in nearly 500 patients with a follow-up period of up to 59 months. The risks and complications associated with this treatment were found to be moderate. Actuarial analysis has demonstrated significant impact on the survival rate of the patients receiving implants with 1 year arrhythmic mortality rate reduced to 2% or less in all groups analyzed. The available data indicate that the automatic cardioverter-defibrillator can reliably identify and correct potentially lethal ventricular tachyarrhythmias, leading to a substantial improvement in survival in properly selected high risk patients.

Adolescent↗
PubMed1985

Recent clinical experience with the automatic implantable cardioverter-defibrillator.

The automatic implantable cardioverter-defibrillator is an electronic device designed to monitor the heart continuously, identify ventricular tachycardias and ventricular fibrillation, and terminate the life-threatening arrhythmias with an internal countershock. This device has been proved to be safe and effective, and its use has led to a significant decrease of arrhythmic mortality in the implantees.

Arrhythmias, Cardiac↗
PubMed1985

Clinical experience with the automatic implantable defibrillator.

Since February 1980, worldwide, over 400 survivors of sudden arrhythmic death have been treated with the automatic implantable defibrillator. Recently, the device has been further improved; it is now a cardioverter-defibrillator (AICD), able to treat ventricular tachycardias as well as ventricular fibrillation. There are two defibrillating electrodes which are used also for waveform analysis; one is located in the superior vena cava, the other is placed over the cardia apex. A third bipolar right ventricular electrode serves for rate counting and R-wave synchronization. When ventricular fibrillation occurs, a 25-joule pulse is delivered; when ventricular tachycardia faster than a preset rate is detected, the discharge is R-wave synchronized. Special batteries can deliver over 100 shocks or provide a three-year monitoring life. Implantation of the device can be achieved through a thoracotomy or by a subxiphoid or a subcostal approach. Thus far, the longest follow-up period has been 58 months. Actuarial analysis shows the one-year mortality attributed to arrhythmias reduced to less than 2%. Thus, the automatic cardioverter-defibrillator can reliably identify and correct potentially lethal ventricular tachyarrhythmias, leading to a substantial increase in survival in properly selected high-risk patients.

Death, Sudden↗
PubMed1978

A chronically implanted system for automatic defibrillation in active conscious dogs. Experimental model for treatment of sudden death from ventricular fibrillation.

Ventricular defibrillation was acheived in active conscious dogs with a chronically implanted automatic system composed of a defibrillator and an alternating current fibrillator. The hermetically sealed defibrillator is encased in titanium, weighs 250 g and has a volume of 145 ml. The sensor continuously monitors ventricular electircal activity and recognizes fibrillation by the absence of isoelectric potential segments. Fibrillation is induced by placing a magnet over the implanted fibrillator. The resulting syncope closely resembles the clinical entity of sudden death, while the defibrillator automatically restores normal rhythm with a truncated exponential pulse of 30 J, 15 seconds after the onset of the arrhythmia. The operational status of the defibrillator can be tested in vitro and noninvasively in vivo with an external analyzer. This experimental model allows for the first time a long-term study of the automatic implantable defibrillator approach to prevent sudden death from ventricular fibrillation under a variety of physiopathologic conditions.

Animals↗
PubMed1978

Treatment of myocardial infarction in a community hospital coronary care unit. Experience with 1,246 patients.

The hospital mortality in 1,246 consecutive acute myocardial infarction patients treated in a large community hospital coronary care unit was 14.4%. Of the total, 52.3% showed no evidence of heart failure, 25.8% had mild to moderate failure, 9.9% had pulmonary edema, and 12% developed cardiogenic shock; the mortality in these groups was 2.2%, 7.4%, 8.9%, and 87.2%, respectively. The mortalitiy in the 1,097 patints who did not have cardiogenic shock was 4.5%. Only one patient died as a result of primary ventricular fibrillation (0.08%). The mortality of complete heart block in the absence of cardiogenic shock (8.3%) was not significantly different from that of comparable patients who did not have complete heart block (4.3%). These results are lower than those generally reported.

Acute Disease↗
PubMed1977

Terminal ECGs.

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Arrhythmias, Cardiac↗
PubMedDate not supplied

Considerations in the development of the automatic implantable defibrillator.

A highly reliable ventricular fibrillation detector and a satisfactory electrode system for delivering defibrillating pulses to the heart play a central role in the development of an automatic implantable defibrillator suitable for clinical use. Among the four implanted electrode designs tested, the combination of an electrode placed in the superior vena cava with a conformal electrode on the apex of the heart provided satisfactory defibrillation thresholds with ease of implantation. A new sensing method is also described for which an electrogram derived from the defibrillating electrodes is used as input. A form of a density function is developed for a filtered version of the input, ventricular fibrillation being characterized by a density curve lacking a large peak occurring at a level corresponding to the baseline of the filtered signal. These ideas are being incorporated into the design of a prototype implantable defibrillator delivering pulses of 24 joules.

Animals↗
PubMedDate not supplied

Coagulation and fibrinolysis in rats poisoned with mercuric chloride.

The effect of mercuric chloride on blood coagulation and fibrinolysis in rats was studied. The mercurial was administered to the animals intragastrically in a single dose of 17.9 mg Hg/kg and the effects were tested on the 1st, 3rd and 7th day. The symptoms of hypercoagulability accompanied by decreased fibrinolytic activity of the plasma were observed in the poisoned rats. The main reason of the lowered fibrinolytic activity seemed to be the inhibition of plasma plasminogen activator or the inhibition of plasminogen activation reaction catalyzed by this enzyme.

Animals↗