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Biomedical subjects

K J Tucker

Publications and source records attributed to K J Tucker.

At least 19 recordsLinked to original sources
PubMed1997

Modification of patient driving behavior after implantation of a cardioverter defibrillator.

Driving habits among recipients of ICDs have not been well characterized previously, yet such information may have implications for development of national policy. This study was undertaken to characterize driving behavior after defibrillator implantation in our patient population. From 1988-1993, 82 ICDs were implanted at the University of Florida. All patients received defibrillator teaching preoperatively and postoperatively with particular emphasis placed on driving restrictions. A standardized questionnaire was developed to ascertain driving behavior, compliance with restrictions, and occurrence of motor vehicle accidents following implantation. The patients were divided into two groups according to whether or not they had received a shock from their device since implantation. Group I patients did, and Group II patients did not. Fifty-two out of 82 (63%, Group I) patients had at least one shock. The remaining 30 patients had received no shocks. Mean age and gender were no different between the two groups. Mean time since implantation was 6 +/- 1.3 years in Group I, compared to 4 +/- 1.5 years in Group II (P = 0.001). Forty-seven out of 52 (90%) and 26 out of 30 (87%) in Groups I and II, respectively, resumed driving after defibrillator implantation. There was no difference in the amount of time that passed prior to resumption of driving. Group I patients drove more, 20.5 +/- 27 miles/day compared to patients in Group II, 8.3 +/- 9.7 miles/day (P = 0.02). No patient experienced device discharge during driving; likewise, no patient was involved in a motor vehicle accident secondary to their device firing. Sixty-seven out of 82 (82%) patients complied with the instructions they thought they heard; seven patients in Group I and eight patients in Group II deliberately did not follow our advice. The majority of patients do comply with physician instructions, although the instructions they remember are not always the instructions given. If a national policy is created to prohibit driving after ICD implantation, effective enforcement may be difficult.

Accidents, Traffic↗
PubMed1996

Transesophageal echocardiographic guidance of transseptal left heart catheterization during radiofrequency ablation of left-sided accessory pathways in humans.

UNLABELLED: Radiofrequency ablation (RFA) of left-sided accessory pathways can be achieved using catheters introduced by a retrograde or transseptal approach. Transesophageal echocardiography (TEE) has previously been demonstrated to be safe and efficacious in guiding transseptal puncture in patients during mitral valvuloplasty (MV). This study was undertaken to assess the feasibility, safety, and clinical utility of TEE during transseptal puncture and RFA of left-sided accessory pathways. METHODS: TEE was performed during transseptal puncture in 30 patients (41 +/- 12 years, 19 females), 15 patients during attempted RFA of a left-sided accessory pathway and 15 patients during attempted balloon MV. RESULTS: There was no difference in age, sex distribution, or procedural complications when MV patients were compared to RFA patients. At baseline, left atrial dimension was increased and congestive heart failure was more common when MV patients were compared to RFA patients (P < 0.05) Adequate baseline two-dimensional and Doppler TEE images were obtained in all patients. One patient sustained mild esophageal bleeding during the TEE. Positioning of the transseptal catheter in the fossa ovalis was facilitated and confirmed by TEE in 29 of 30 cases. One case of cardiac perforation occurred and was associated with inadequate TEE localization of the fossa ovalis. Thrombus was detected on the transseptal catheter by TEE in two cases prior to systemic heparinization. In both cases, thrombus was removed without embolic event. CONCLUSIONS: TEE safely guides transseptal puncture in patients undergoing RFA of left-sided accessory pathways. TEE markers of the fossa ovalis facilitate puncture and may reduce the risk of cardiac perforation particularly in patients with a normal size left atrium. TEE may be especially valuable for identifying thrombus during transseptal puncture.

Adolescent↗
PubMed1995

Emergency intracardiac defibrillation for refractory ventricular fibrillation.

Hemodynamically unstable ventricular arrhythmias induced during electrophysiologic testing almost always respond to prompt application of direct current transthoracic shocks. In rare cases, however, ventricular fibrillation may be refractory to conventional treatment. Recently, a technique of intracardiac defibrillation has been successfully used to resuscitate patients with ventricular fibrillation refractory to transthoracic defibrillation. We describe two patients with a history of myocardial infarction and left ventricular dysfunction who were admitted with symptomatic episodes of ventricular tachycardia. Both had inducible sustained monomorphic ventricular tachycardia. During a repeat electrophysiologic study in Patient No. 1 on procainamide and at the initial study in Patient No. 2, right ventricular burst pacing to terminate ventricular tachycardia resulted in ventricular fibrillation refractory to resuscitation efforts, including transthoracic defibrillation with 360 J. Emergency intracardiac defibrillation with 200 and 360 J, respectively, successfully converted both patients to sinus rhythm. Both patients were subsequently discharged from the hospital on amiodarone. These cases illustrate the life-saving capabilities of intracardiac defibrillation.

Aged↗
PubMed1995

Advanced cardiac life support: update on recent guidelines and a look at the future.

The objectives of this article are to provide an update of the American Heart Association (AHA) 1992 National Conference guidelines for cardiopulmonary resuscitation (CPR) and emergency cardiac care and to review the investigation and development of new methods of CPR which may be considered in future recommendations. Despite an organized approach to sudden cardiac arrest, survival in patients receiving CPR is in the range of 5-15%. The new AHA guidelines recommend standard manual CPR performed at a rate of 80-100 compressions/min and organized algorithms of advanced cardiac life support. These guidelines stress widespread community training and rapid response in the following sequence: (1) recognition of early warning signs, (2) activation of the emergency medical system (EMS), (3) basic CPR, (4) early defibrillation, (5) intubation, and (6) intravenous medication. Several new recommendations pertain specifically to in-hospital care and are, therefore, particularly relevant to physician management of cardiac arrest. The best predictor of survival in patients requiring circulatory support after cardiac arrest is attainable coronary and cerebral perfusion. Unfortunately, the minimal levels of end-organ perfusion required to sustain life are often difficult or impossible to achieve with standard manual cardiopulmonary resuscitation and several new techniques have therefore been introduced. The most promising of these techniques are (1) interposed abdominal compression, (2) pneumatic vest, and (3) active compression-decompression resuscitation. Each of these techniques offers unique advantages when compared with standard manual cardiopulmonary resuscitation. The 1992 National Conference recommendations provide a rational framework for the resuscitation of cardiac arrest victims. New methods of cardiopulmonary resuscitation are now available and investigation into these methods continues.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1995

Abnormal pulmonary artery pressure profile after cardiac transplantation: an exercise Doppler echocardiographic study.

This study was designed to test the hypothesis that pulmonary artery pressure at rest and during exercise differs between patients with a transplanted heart and normal subjects and to determine the mechanisms responsible for the difference. Twenty-one patients who had undergone heart transplantation 1.5 to 27 months earlier without current evidence of acute cardiac rejection and 25 normal subjects were studied by exercise Doppler echocardiography. Systolic pulmonary artery pressure was higher at baseline in heart transplant patients than in normal subjects, at 31.6 +/- 9 mm Hg (mean +/- SD) versus 22.5 +/- 4, respectively (p = 0.0001). The increase in systolic pulmonary artery pressure with exercise was 1.4 times higher in heart transplant patients and correlated with pretransplantation pulmonary vascular resistances (r = 0.55; p = 0.01). In contrast, cardiac index at baseline or during exercise did not differ between the two groups. Diastolic parameters and ejection fraction at baseline or during exercise did not correlate with systolic pulmonary artery pressure. In conclusion, Doppler exercise echocardiography offers an alternative, safe method hemodynamic study of the transplanted heart. Although an abnormal increase in left ventricular filling pressure with exercise has been well documented, further studies are needed to investigate and characterize potential abnormalities in pulmonary vascular tone in the transplanted heart.

Adult↗
PubMed1995

Motor vehicle accidents in patients with an implantable cardioverter-defibrillator.

OBJECTIVES: This study was designed to examine driving safety in patients at risk for sudden death after implantation of a cardioverter-defibrillator. BACKGROUND: Cardioverter-defibrillators are frequently implanted in patients at high risk for sudden death. Despite concern about the safety of driving in these patients, little is known about their actual motor vehicle accident rates. METHODS: Surveys were sent to all 742 physicians in the United States involved in cardioverter-defibrillator implantation and follow-up. Physicians were questioned about numbers of patients followed up, numbers of fatal and nonfatal accidents, physician recommendations to patients about driving and knowledge of state driving laws. RESULTS: Surveys were returned by 452 physicians (61%). A total of 30 motor vehicle accidents related to shocks from implantable defibrillators were reported by 25 physicians over a 12-year period from 1980 to 1992. Of these, nine were fatal accidents involving eight patients with a defibrillator and one passenger in a car driven by a patient. No bystanders were fatally injured. There were 21 nonfatal accidents involving 15 patients, 3 passengers and 3 bystanders. The estimated fatality rate for patients with a defibrillator, 7.5/100,000 patient-years, is significantly lower than that for the general population (18.4/100,000 patient-years, p < 0.05). The estimated injury rate, 17.6/100,000 patient-years, is also significantly lower than that for the general public (2,224/100,000 patient-years, p < 0.05). Only 10.5% (30 of 286) of all defibrillator discharges during driving resulted in accidents. Regarding physician recommendations, most physicians (58.1%) ask their patients to wait a mean (+/- SD) of 7.3 +/- 3.4 months after implantation or a shock before driving again. CONCLUSIONS: The motor vehicle accident rate caused by discharge from an implantable cardioverter-defibrillator is low. Although restricting driving for a short period of time after implantation may be appropriate, excessive restrictions or a total ban on driving appears to be unwarranted.

Accidents, Traffic↗
PubMed1994

Cardiopulmonary resuscitation. Historical perspectives, physiology, and future directions.

PURPOSE: To review the historical evolution and rationale for the development of new techniques of cardiopulmonary resuscitation (CPR). DATA SOURCES: English-language studies published after 1960 were identified by computer and manual search using MEDLINE and Index Medicus. Historical references were obtained through a HISTLINE search. Additional information was acquired from personal files and bibliographies of existing literature. STUDY SELECTION: Critical review with emphasis on study size, methods, and reproducibility of results. RESULTS: Survival after in-hospital cardiac arrest and institution of CPR is approximately 10% to 15%. Investigation of the physiology of blood flow during CPR has led to the conclusion that flow may occur because of direct cardiac compression or thoracic pump forces. Based on these observations, several new techniques of CPR have been introduced. Interposed abdominal compression, pneumatic vest, and active compression-decompression resuscitation have been shown to improve cardiopulmonary hemodynamics in animal models and humans after cardiac arrest. Only interposed abdominal compression CPR has been shown to improve long-term survival in human subjects after in-hospital cardiac arrest. Although these techniques have shown promising results in animal studies and a limited number of clinical trials, none has gained widespread use. CONCLUSIONS: Improved methods of CPR are now available. Selective use of CPR in the hospital and community training in the use of these new adjunctive techniques should have the greatest impact on improved survival after sudden cardiac arrest.

Cardiopulmonary Resuscitation↗
PubMed1994

Clinical and laboratory investigations of active compression-decompression cardiopulmonary resuscitation.

Based upon an anecdotal report of successful resuscitation using a toilet plunger, Cohen and co-workers have developed and investigated a hand-held suction cup as an adjunct to standard manual CPR. This new method, called active compression-decompression cardiopulmonary resuscitation, utilizes a device which is placed over the mid-sternum, approximately 1-2 inches above the lower rib cage border. Active compression-decompression cardiopulmonary resuscitation is then performed in accordance with American Heart Association guidelines at a rate equal to 80-100/min using a 50% duty cycle and compression depth of 1.5-2.0 inches. Initial studies using the ACD device in both models and human subjects late after cardiac arrest have demonstrated improved cardiopulmonary hemodynamics when compared to standard manual CPR. Transophageal echocardiographic studies in human subjects have shown increased left ventricular filling during active decompression suggesting that active chest decompression improves venous return to the heart thus increasing left ventricular volume and stroke volume. Improved resuscitation success has also been documented in human subjects after in-hospital and pre-hospital cardiac arrest. Active compression-decompression cardiopulmonary resuscitation is a simple method which utilizes a hand held suction cup as an interface between rescuer and victim during closed chest circulatory support. This method allows for standard manual cardiopulmonary resuscitation with the addition of active chest wall decompression and appears to be a beneficial adjunct to standard manual cardiopulmonary resuscitation.

Blood Flow Velocity↗
PubMed1994

Changes in arterial and mixed venous blood gases during untreated ventricular fibrillation and cardiopulmonary resuscitation.

This investigation was designed to evaluate the changes in arterial and mixed venous acid-base conditions during untreated ventricular fibrillation and after institution of cardiopulmonary resuscitation (CPR). Fifty-two swine (weight: 25-40 kg) were studied after induction of ventricular fibrillation. In a subgroup of 10 animals, 10-min CPR trials were performed. Arterial and mixed venous blood gases were monitored at baseline, after 5 min of untreated ventricular fibrillation (nonintervention interval) and after 10 min of mechanical CPR. Standard CPR was performed at compression rates of 100/min with a 60% duty cycle. Arterial pH, Pco2, and HCO3 were unchanged when baseline values were compared with those obtained after 5 min of untreated ventricular fibrillation, while arterial Po2 decreased from 81 to 69 torr. Mixed venous pH decreased from 7.41 to 7.35, Pco2 increased from 43 to 48 torr, Po2 decreased from 40 to 38 torr and HCO3 decreased from 28 to 26 mEq/l (P < 0.05). Although these changes were statistically significant, many remain in the normal range. Both arterial and mixed venous pH and HCO3 fell further after 9 min of CPR and Pco2 increased (P < 0.05). Alterations in mixed venous pH and Pco2 were more apparent than corresponding changes in arterial blood gas composition. We conclude that untreated cardiac arrest may be accompanied by normal arterial and mixed venous blood gas levels. Tissue acidosis is only revealed after tissue perfusion is restored and is most accurately reflected in the mixed venous blood gas composition. This apparent paradox provides insight into the relationship between tissue perfusion and arterial and mixed venous acid-based composition.

Acid-Base Equilibrium↗
PubMed1994

Active compression-decompression resuscitation: effect on resuscitation success after in-hospital cardiac arrest.

OBJECTIVES: The purpose of this study was to test the hypothesis that active compression-decompression would improve resuscitation success in human subjects after cardiac arrest. BACKGROUND: Active compression-decompression cardiopulmonary resuscitation is a new method that improves cardiopulmonary hemodynamic function in animal models and humans after cardiac arrest. METHODS: We conducted a prospective randomized clinical trial in patients with in-hospital cardiac arrest. Patients were assigned to receive standard manual or active compression-decompression cardiopulmonary resuscitation. The primary study end points were spontaneous return of circulation, 24-h survival and survival to hospital discharge. RESULTS: Fifty-three consecutive patients after cardiac arrest undergoing 64 resuscitation attempts were studied (30 women, 23 men; mean [+/- SD] age 71 +/- 13 years, range 38 to 96). Spontaneous return of circulation was observed in 24 (47%) of 53 patients and was increased in patients receiving active compression-decompression compared with those receiving standard manual cardiopulmonary resuscitation (15 [60%] of 25 vs. 9 [32%] of 28, respectively, p = 0.042); 24-h survival was increased (12 [48%] of 25 vs. 6 [21%] of 28, respectively, p = 0.041); and there was a trend toward improved survival to hospital discharge (6 [24%] of 25 vs. 3 [11%] of 28, respectively, p = 0.198) when active compression-decompression was compared with standard manual cardiopulmonary resuscitation. CONCLUSIONS: Active compression-decompression cardiopulmonary resuscitation improves return of spontaneous circulation and 24-h survival after in-hospital cardiac arrest. Active compression-decompression cardiopulmonary resuscitation appears to be a beneficial adjunct to standard manual cardiopulmonary resuscitation.

Aged↗
PubMed1994

The biphasic mechanism of blood flow during cardiopulmonary resuscitation: a physiologic comparison of active compression-decompression and high-impulse manual external cardiac massage.

STUDY OBJECTIVE: Dismal survival in patients receiving standard manual CPR provided the rationale for the investigation of alternate methods of closed-chest circulatory support. Active compression-decompression (ACD) and high-impulse CPR are alternatives to standard manual CPR. This study was designed to test the hypothesis that ACD CPR provides superior cardiopulmonary hemodynamics due to an active decompression phase when compared with high-impulse manual CPR. PARTICIPANTS: Hemodynamics were studied during ACD and high-impulse CPR in eight adult beagles. DESIGN: Four animals were chronically instrumented and four were studied acutely. In an additional four animals, ACD was compared with sham ACD CPR. Each CPR technique was performed sequentially for 2 minutes, in random order, at a rate of 120, 50% duty cycle, and 1.5 to 2.0 in of compression depth. Measurements obtained included aortic, right atrial, left ventricular, and coronary perfusion pressures (in mm Hg); pulmonary artery flow, and left ventricular dimension. RESULTS: ACD maximized cardiopulmonary hemodynamics, including coronary perfusion pressure and stroke volume, compared with both high-impulse manual and sham ACD CPR. ACD CPR also increased left ventricular pressure change per unit time during decompression, and these changes correlated well with left ventricular volume changes. CONCLUSION: In the intact dog, ACD CPR generates physiologically and statistically superior hemodynamics when compared with high-impulse manual CPR. Improved blood flow seems to be related to more efficient ventricular filling and emptying. These findings emphasize the biphasic nature of CPR and the importance of active decompression.

Animals↗
PubMed1994

The composition of gas given by mouth-to-mouth ventilation during CPR.

STUDY OBJECTIVE: To compare the concentration of a rescuer's exhaled O2 and CO2 during mouth-to-mouth ventilation with or without chest compression. DESIGN: Prospective repeated measures study. Simulated one- and two-rescuer cardiopulmonary resuscitation (CPR) was performed as recommended by the American Heart Association. SETTING: University laboratory. PARTICIPANTS: Fifty-five healthcare professionals certified in basic and advanced cardiac life support volunteered as rescuers in this study. MEASUREMENTS AND RESULTS: Thirty-three volunteers performed one-rescuer CPR, and 22 volunteers performed two-rescuer CPR. Minute ventilation for both groups increased 50% to 130% during CPR (p < 0.05). During the performance of CPR, the concentration of exhaled O2 increased from 16.4 +/- 0.7% to 16.9 +/- 0.5% in the one-rescuer CPR group and from 16.5 +/- 0.9% to 17.8 +/- 0.6% in the two-rescuer CPR group (p < 0.05). The concentration of exhaled CO2 in the one-rescuer CPR group did not change significantly throughout the entire experiment, but decreased in the two-rescuer CPR group from a baseline measurement of 4.0 +/- 0.6% to 3.5 +/- 0.4% (p < 0.05). During CPR, the concentration of exhaled CO2 was 4.0 +/- 0.4% in the one-rescuer CPR group compared with 3.5 +/- 0.4% in the two-rescuer CPR group (p < 0.05). CONCLUSIONS: The gas given by mouth-to-mouth ventilation is a hypercarbic and hypoxic mixture compared with room air. Mouth-to-mouth ventilation is the only circumstance in which a hypercarbic and hypoxic gas is given as therapy. Further laboratory and clinical studies are necessary to determine the effect of mouth-to-mouth ventilation during CPR.

Carbon Dioxide↗
PubMed1993

Active compression-decompression resuscitation: analysis of transmitral flow and left ventricular volume by transesophageal echocardiography in humans. Cardiopulmonary Resuscitation Working Group.

OBJECTIVES: This study was designed to test the hypothesis that active compression-decompression cardiopulmonary resuscitation increases transmitral flow and end-decompression left ventricular volume over levels achieved with standard manual cardiopulmonary resuscitation. BACKGROUND: Recently, cardiopulmonary resuscitation incorporating active compression and decompression of the chest has been demonstrated to improve hemodynamic status in a canine model and in humans after cardiac arrest. METHODS: The active compression-decompression device was applied midsternum in five consecutive patients and results compared sequentially (in random order) with those of standard manual cardiopulmonary resuscitation. Both techniques were performed at 80 compressions/min with a 1.5- to 2-in. (3.8 to 5.1 cm) compression depth and a 50% duty cycle. Transesophageal echocardiographic data obtained in each patient included the velocity-time integral of transmitral pulsed Doppler recordings and two-dimensional images of the left ventricle in the long-axis view. Planimetric volume measurements of the left ventricle were obtained at both end-compression and end-decompression. RESULTS: No difference was observed in end-compression volume between the two techniques (p = 0.81). Increased end-decompression volume (active compression-decompression technique 81.3 +/- 12.5 vs. standard technique 69.4 +/- 10.8, p < 0.05), stroke volume (active compression-decompression technique 32.6 +/- 6.8 vs. standard technique 17.6 +/- 5.2, p < 0.05) and velocity-time integral of transmitral flow (active compression-decompression technique 15.8 +/- 4.3 vs. standard technique 7.8 +/- 2.3, p < 0.05) were found in the active compression-decompression group. The transmitral velocity-time integral was highly correlated with left ventricular stroke volume (r = 0.90). CONCLUSIONS: Improved transmitral flow, end-decompression left ventricular volume and stroke volume are seen with active compression-decompression resuscitation, suggesting a biphasic cardiothoracic cycle of flow. Active decompression of the chest appears to be a beneficial adjunct to standard cardiopulmonary resuscitation.

Aged↗