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At least 145 records · Page 8Linked to original sources
PubMed2005

Are there surgical implications to aortic root motion?

BACKGROUND AND AIM OF THE STUDY: By increasing the longitudinal stress in the ascending aorta, downward movement of the aortic root might promote the proximal transverse tears seen in aortic dissections. The study aim was to evaluate the influence of five common cardiac conditions on the magnitude of aortic root displacement in cardiac patients. METHODS: Aortic root contrast injections were analyzed in 90 patients (mean age 68 years) to measure downward motion of the root perpendicular to the plane of the sinotubular junction (STJ). RESULTS: Displacement of the aortic root ranged from 0 to 14 mm (mean 4.8 mm). Patients with aortic insufficiency (AI) showed increased aortic root movement (7.3 versus 4.3 mm, p = 0.003), whereas those with left ventricular hypokinesis (3.7 versus 5.5 mm, p = 0.014) or with myocardial hypertrophy (3.8 versus 5.1 mm, p = 0.073) exhibited reduced downward movement. These variables were independent, and correlated with the magnitude of aortic root motion. A stress analysis of the aortic root, arch and branches of the arch determined that the longitudinal stress approximately 2 cm above the STJ, in the outer curve of the aorta, was increased by 32% in patients with AI compared to patients without AI. CONCLUSION: Patients with cardiac conditions associated with increased aortic root motion such as AI may be at greater risk of aortic dissection because of increased longitudinal stress in the ascending aorta. Therefore, AI should be used as an indicator and aortic root displacement monitored to prevent the risk of aortic dissection.

Adult↗
PubMedDate not supplied

Investigation of the models of electrical field generated by the heart for cardiac surgery conditions.

In this work the investigations of the electrical field generated by the heart, carried out using a computer simulation method are presented. Two models have been constructed approximating the chest region for the following conditions: (a) normal heart activity, and (b) open chest during the cardiac surgery. For the above models the distribution of potentials on the heart surface are determined. The source field investigated takes the following forms: dipole, multidipole, and multipole. Numerical experiments for these models show a difference between normal heart activity and of the heart in the condition when the chest is open during surgery.

Cardiac Surgical Procedures↗
PubMed1994

Increased G-suit coverage improves cardiac preloading conditions during positive pressure breathing.

A miniaturized nuclear probe (MNP) and multiple gated cardiac blood pool imaging (RCBI) were used to measure left ventricular function during positive pressure breathing (PPB) while wearing an extended-coverage (EC) vs. standard-coverage (SC) anti-G-suit. Seven subjects were exposed to 4.0 and 9.3 kPa PPB wearing each anti-G-suit during 3 min of PPB at ground level. Ejection fraction was unchanged using both techniques. The atrial component to diastolic filling was greater with the SC suit (p < 0.02). Using the MNP, end-diastolic and end-systolic volumes declined non-linearly over time at both PPB levels; these declines were greater with the SC G-suit (p < 0.001). Left ventricular preload declines during PPB. This is attenuated with increased G-suit coverage, confirming prior results using impedance cardiography. RCBI is less sensitive than MNP's for measuring non-steady-state cardiac physiology such as PPB.

Adult↗
PubMed1996

Cardiac surgical conditions induced by beta-blockade: effect on myocardial fluid balance.

BACKGROUND: Both crystalloid and blood cardioplegia result in cardiac dysfunction associated with myocardial edema. This edema is partially due to the lack of myocardial contraction during cardioplegia, which stops myocardial lymph flow. As an alternative, acceptable surgical conditions have been created in patients undergoing coronary artery bypass operations with esmolol-induced minimal myocardial contraction. We hypothesized that minimal myocardial contraction during circulatory support using either standard cardiopulmonary bypass (CPB) or a biventricular assist device would prevent myocardial edema by maintaining cardiac lymphatic function and thus prevent cardiac dysfunction. METHODS: We placed 6 dogs on CPB and 6 dogs on a biventricular assist device and serially measured myocardial lymph flow rate and myocardial water content in both groups and preload recruitable stroke work only in the CPB dogs. In all dogs we minimized heart rate with esmolol for 1 hour during total circulatory support. RESULTS: Although myocardial lymph flow remained at baseline level during CPB and increased during biventricular assistance, myocardial water accumulation still occurred during circulatory support. However, as edema resolved rapidly after separation from circulatory support, myocardial water content was only slightly increased after CPB and biventricular assistance, and preload recruitable stroke work was normal. CONCLUSIONS: Our data suggest that minimal myocardial contraction during both CPB and biventricular assistance supports myocardial lymphatic function, resulting in minimal myocardial edema formation associated with normal left ventricular performance after circulatory support. The concept of minimal myocardial contraction may be a useful alternative for myocardial protection, especially in high-risk patients with compromised left ventricular function.

Adrenergic beta-Antagonists↗
PubMed1985

The effect of cardiac autonomic blockade on ventricular response to changes in preload.

Echocardiographic (E) assessment of left ventricular response to increases (I) and decreases (D) in preload of 9 volunteer male subjects (mean age 25 +/- 2.0 years) was made during both control (C) and cardiac blocked (B) conditions. Cardiac autonomic blockade was produced by intravenous administration of atropine (0.04 mg/kg) and propranolol (0.2 mg/kg), while I was produced by 5 degrees head-down tilt (T) for 90 min and D by lower body negative pressure to -40 Torr. Increases in resting heart rate of 44% and diastolic blood pressure of 13% occurred after B, (P less than 0.05). During C, the alterations in preload produced mean changes in end-diastolic volume (EDV) ranging from 135 +/- 10 cm3 for I to 96 +/- 9.1 cm3 for D. Changes in stroke volume during condition C were significantly related to changes in EDV during preload alterations and conformed to a normal LV function curve and were described by SV = 0.6 EDV + 4.5 cm3 (r = 0.85; P less than 0.001). Similarly during B, SV = 0.43 EDV + 5.8 cm3 (r = 0.75; P less than 0.001). Comparison of the LV function curves produced during C and B showed that both slope of regression and r were significantly different (P less than 0.01). These data indicate that cardiac autonomic blockade produces a downward shift in the LV function curve indicating a depression in myocardial contractility. In addition, the data indicate that changes observed in LV function during wide variations in preload are independent of autonomic nervous system influences and are independent of the intrinsic heart rate.

Adult↗
PubMed1997

Inhibition of malignant cell proliferation by culture media conditioned by cardiac or skeletal muscle.

The present work is an attempt to explain the high resistance of muscles to cancer development. We used primary cultures of rat skeletal and cardiac muscle, and examined the effect of the supernatant of these cultures (conditioned medium; CM) on proliferation of cancer cells. The results demonstrated that CM inhibited the proliferation of several types of malignant cells by more than 50%, without a significant inhibition on normal cells. Cell cycle analysis revealed that CM increased the number of cells in S and G2 phases, suggesting a cytostatic effect of CM. For defining the biological properties of the factor(s) which are present in the CM, skeletal muscle cultures were grown in chemically defined medium (serum free medium). The concentrated sample was applied to a Sephadex G-50 column and three fractions were obtained. Only one fraction showed inhibitory activity. Four protein bands were observed in this fraction, as revealed by SDS-PAGE. We suggest that some, or all of these proteins are responsible for inhibition of tumor cell replication.

Analysis of Variance↗
PubMed2002

Importance of emergency identification schemes.

BACKGROUND: Millions of people worldwide may have a hidden medical condition that could endanger their life in an emergency. These conditions may include cardiac conditions, severe allergies, or diabetes. Emergency identification schemes such as Medic Alert produce emblems that alert health care professionals to potential problems and can ensure appropriate and prompt treatment. This paper uses mechanical failure of the Björk-Shiley convexo-concave (BSCC) heart valve as an example of a hidden medical condition. These patients have been encouraged to carry information to alert staff in an emergency that they have a BSCC patient in their care and to be alert to the signs and symptoms of acute valve malfunction. OBJECTIVE: To establish awareness and credibility of emergency identification schemes among emergency personnel and to assess if information on specific medical conditions would influence ambulance personnel regarding destination hospitals. METHODS: Questionnaires were sent to senior staff (n=380) of accident and emergency (A&E) departments and operational directors of ambulance headquarters (n=39) throughout the United Kingdom. Hospitals were divided into regional divisions to assess differences in responses across regions. RESULTS: The majority of respondents (99%) had heard of emergency identification schemes and felt that it was important for patients with special conditions to carry some form of identification. Nearly all ambulance respondents (97%) indicated it was routine to search for body worn emblems in contrast with only 71% of A & E staff. However, more than half of ambulance respondents (53.9%) stated information on emblems/cards would not influence their choice of destination hospital. CONCLUSIONS: The importance of how information on pre-existing medical conditions can influence care, is highlighted by the BSCC valve issue, where immediate diagnosis is essential for patient survival. It is vital that all staff routinely search patients for this information and if necessary act upon the information provided.

Emergency Medical Services↗
PubMed1988

Sudden death during exercise: how real a hazard?

The literature dealing with sudden cardiac death in relation to exercise, particularly sport, is reviewed. The exact incidence of unexpected sudden cardiac death during physical activity in persons previously presumed healthy is difficult to determine due to the wide variation in reporting methods; by all indications, it is extremely low. The most common cardiac condition underlying sudden cardiac death in persons over age 30 years is, overwhelmingly, coronary artery disease. In younger athletes it is much less common and is usually due to hypertrophic cardiomyopathy, congenital anomalies or inherent abnormalities of the conducting system. The PAR-Q (Preparation for Activity Readiness Questionnaire) appears to be an adequate pre-exercise screening tool for recreational and middle-aged athletes. A (cost) effective pre-exercise screening strategy for the younger and highly competitive athlete remains elusive. Extensive and costly screening methods (eg, ECG, echocardiography, treadmill studies) do not seem warranted for any asymptomatic, presumed healthy groups. Although the risk of sudden cardiac death is measurably higher during exercise than during sedentary activity, the overall risk is demonstrably lower in habitually active and physically fit persons. The resolution of this paradox is that even the most active persons rarely spend more than an hour or two a day at vigorous exercise, while the protective effects against sudden cardiac death operate for the remainder of the day.

Canada↗
PubMed1993

Prosthetic valve function under simulated low cardiac output conditions: preliminary observations.

An experimental protocol was developed and a series of laboratory experiments started to assess the function and behaviour of replacement valves under simulated low cardiac output, that is low flow and low pressure conditions. The Helmholtz Institute's pulse duplicator (1) and instrumentation were carefully tuned in order to achieve accurate and reproducible delivery of the required extremely small stroke volumes. A pilot study was completed with 27 mm St. Jude Medical and CarboMedics bileaflet valves and Wessex porcine bioprostheses, three each, in the simulated aortic position. The results of these experiments suggest that the performances of the two bileaflet prostheses are inadequate if the flow is less than 2.0 l/min; the porcine bioprosthesis needs relatively low flow to start proper function, but its stenotic nature soon becomes apparent; increase in pressure without a corresponding increase in flow has a deleterious effect on valve performances by increasing regurgitation; increasing pulse rate is inversely correlated with valve efficiency; and there is no "all-or-none" cut off point between functional and non-functional situation for the tested devices; there is a semilogarithmic relation between increasing flow and valve performance. The clinical consequences are manifold and may be related both to the stabilization of circulation and to the increased thromboembolic risk during the early postoperative period.

Bioprosthesis↗
PubMed1998

Comparison of cardiac findings at necropsy in octogenarians, nonagenarians, and centenarians.

Certain clinical and necropsy cardiac findings are described and compared in 391 octogenarians (80%), 93 nonagenarians (19%), and in 6 centenarians (1%). The number of men and women was similar (248 [51%] and 242 [49%]). The cause of death was cardiac in 228 patients (47%), vascular but noncardiac in 71 (14%), and noncardiac and nonvascular in 191 (39%). The frequency of a cardiac condition causing death decreased with increasing age groups (51% vs 32% vs 0), and the frequency of a noncardiac, nonvascular condition causing death increased with increasing age groups (36% vs 47% vs 100%). Among the cardiac conditions causing death, coronary artery disease was found in 62% of cases (141 of 228), aortic valve stenosis in 16% (36 of 228), and cardiac amyloidosis in 10% of cases (22 of 228). Calcific deposits were found at necropsy in the coronary arteries in 81% of the patients (398 of 490), in the aortic valve in 47% (228 of 490), in the mitral annular area in 39% of the patients (190 of 490), and in 1 or both left ventricular papillary muscles in 25% of the patients (122 of 490). The calcific deposits tended to be less frequent in the octogenarians. Three hundred (61%) of the 490 patients had > or = 1 major coronary arteries narrowed > 75% in cross-sectional area by plaque and the percent of patients in each of the 3 age groups and the percent of coronary arteries significantly narrowed in each of the 3 age groups were similar.

Age Factors↗
PubMedDate not supplied

Experimental psychogenic hypertension: blood pressure changes conditioned to painful stimuli (schizokinesis).

1. During habituation in 4 dogs to a new environment and attachment of apparatus, the blood pressure was at first high but fell from about 175 systolic the first day to about 135 on the ninth day. 2. In the first group of dogs used two years previously to form 3 cardiac conditional reflexes to 3 intensities of shock, the blood pressure measured after a 13-month rest was retained and specific to the 3 intensities of shock. In another group of 2 dogs the blood pressure was specific to the excitatory and to the inhibitory signals for pain. 3. The conditioned hypertension was parallel to the conditioned heart rate. 4. The conditioned hypertension was parallel to the motor conditional reflex with certain exceptions: the conditioned hypertension was, like the cardiac conditional reflex, quicker to form and more persistent, thus being present often in the absence of the motor conditional reflex--an evidence of schizokinesis. 5. The conditioned hypertension was retained for a 13-month rest period without intervening training, being present immediately when the dog was brought back into the environment where the stress had been given. 6. Although the conditioned hypertension was retained in the long rest period, it could in one dog be reduced somewhat by repeating the conditional stimulus without the shock (non-reinforcement), a more efficient way of extinction than simple rest. In another dog the hypertension became exaggerated though there was no repetition of the stress, showing evidence of an internal development (autokinesis). 7. The amplitude of the conditioned hypertension varied according to the individual dog from about 130 average control to limits of 150 to 225 (conditioned hypertension) in the separate dogs.

Animals↗
PubMed1994

[Role of the family practitioner in the management of patients following a myocardial infarct].

OBJECTIVE: Determining the role of the general practitioner (GP) in the management of the postinfarction patient, the factors that influence this role, and the relation between GP and cardiologist. DESIGN: Descriptive. SETTING: Registration Network of Family Practice (RNF) of the University of Limburg, the Netherlands. METHOD: Data were obtained from a sample of 284 patients from 30 GPs, all participating in the RNF. The GPs completed a questionnaire about their own patients while the data concerning the cardiac state of the patients were obtained from their problem lists. RESULTS: Postinfarction care was given in only 50% of the patients. Relatively more patients with a more severe cardiac condition were under regular medical follow-up than those with a less severe cardiac condition. However, the severity of the disease had no effect on the specialty of the doctor performing the follow-up (GP or cardiologist), nor had the time expired after the myocardial infarction. In almost 50% of the cases the GPs found continuation of the follow-up by the cardiologist not necessary, in 25% of the cases they were not satisfied with the complementary roles of both disciplines. CONCLUSION: Postinfarction care by the GPs was not uniform. They need guidelines for the management of such patients, based on the patient's risk profile. There is a need for better coordination between GP and cardiologist.

Aftercare↗
PubMed1996

Cardiac effects of standard-dose halofantrine therapy.

The antimalarial drug halofantrine hydrochloride has been associated with cardiac arrhythmias. This is a report of a study on the cardiac effects of standard-dose halofantrine (24 mg/kg) on a sample of 48 patients selected from a group of 402 Dega (Montagnard) refugees treated for Plasmodium falciparum infection. Prolongation of the rate-corrected QT interval (QTc) on the electrocardiogram (ECG) was used as an indicator of risk for halofantrine-associated cardiac arrhythmias. We found that standard-dose halofantrine was associated with a lengthening of the mean QTc from 0.04 sec(1/2) to 0.44 sec(1/2). Two patients had a QTc increase of greater than 25%, but none had a follow-up QTc of more than 0.55 sec(1/2), an interval length generally considered to be a risk factor for ventricular arrhythmias. Regression analysis indicated that pretreatment ECGs were poorly predictive of QTc lengthening during therapy, although pretreatment ECGs may be useful to evaluate patients with pre-existing cardiac conditions. The manufacturer has recommended that the halofantrine dose not exceed 24 mg/kg and revised the list of medication contraindications to include some cardiac conditions. Clinicians should weigh a patient's risk, including history of cardiac disease and availability of alternative therapy before use of halofantrine.

Adolescent↗
PubMed1987

Survey of underlying conditions of persons hospitalized with acute respiratory disease during influenza epidemics in Houston, 1978-1981.

The peak occurrence of hospitalizations of persons with acute respiratory disease (ARD), usually pneumonia, has coincided with the peak of influenza virus activity each year. The purpose of this study was to examine the diagnoses other than ARD on the discharge record of patients hospitalized with ARD. We were particularly interested in determining the frequency of high-risk conditions for which influenza vaccine is currently recommended. The risk for ARD hospitalization was 19.7 per ten thousand for persons with high-risk conditions and only 9.3 for persons without. Chronic pulmonary disorders were the most common underlying conditions identified, and persons with pulmonary conditions had the greatest risk for ARD hospitalization. The highest rate occurred among persons older than 65 yr of age with pulmonary conditions (87.5 per ten thousand), and the rate was 27.5 for persons 45 to 64 yr of age. Cardiac conditions were the second most frequent group of underlying disorders of patients hospitalized with ARD. Only for persons younger than 20 yr of age was the risk of ARD hospitalization greater for persons with cardiac conditions than for those with pulmonary conditions (22.9 and 14.9 per ten thousand, respectively). Death, however, was more frequent among persons with underlying heart disease. Intensified effort is needed to fully implement recommendations for prophylaxis of influenza in order to reduce these risks.

Acute Disease↗