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Biomedical subjects

H D Allen

Publications and source records attributed to H D Allen.

At least 55 records · Page 3Linked to original sources
PubMed1991

ACC/AHA guidelines for cardiac catheterization and cardiac catheterization laboratories. American College of Cardiology/American Heart Association Ad Hoc Task Force on Cardiac Catheterization.

It is evident that the practice of cardiac catheterization has undergone, and continues to undergo, marked change. Most prominent are the recent very rapid proliferation of catheterization laboratories in general and the development of newer types of catheterization laboratory. No uniform definitions exist for these newer laboratories, so meaningful communication is difficult. The new settings are of particular concern because their location, mobility, organization, and ownership raise questions about the quality of patient care. Most difficult to address are the questions about patient safety and physician conflict of interest. There are no objective data in peer-reviewed literature to support the reported safety and cost savings of these newer settings. Through deliberations, surveys, interviews, and correspondence with the cardiology community embraced by the ACC and the AHA, the task force generally found that in freestanding catheterization laboratories, access to emergency hospitalization may be delayed, and appropriate oversight may be lacking. Additionally, opportunities for self-referral may be fostered and the perception of commercialism and entrepreneurial excess in practice created. All of these problems must be avoided. The growth and development of some freestanding facilities, particularly the mobile laboratories, do not seem to have been driven by an increased need in remote communities or for temporary support but rather almost exclusively by a desire to capture market share. Accordingly, a series of definitions, guidelines, and recommendations for the laboratories as well as for patient selection has been developed. The consensus was that a very restrictive and cautious attitude to the newer settings is appropriate at this time. The justification for development or expansion of cardiac catheterization services must be patient need. Documentation of this need must be based on objective estimates of the number of patients with known or suspected cardiac disease who meet generally accepted indications for laboratory study. Concerns about the lack of data from prospective clinical trials of patient safety in such a group necessitate a very cautious attitude toward any new catheterization services, in particular those without in-house cardiac surgical support. In view of the lack of appropriately controlled safety and need data for hospital-based, mobile, or freestanding laboratories operating without on-site (accessible by gurney) cardiac surgery facilities, the task force reaffirms the position that further development of these services cannot be endorsed at this time. In addition, there is reason for major concern that such proliferation in catheterization services may contribute to increasing costs and troubling ethical questions.

American Heart Association↗
PubMed1990

Balloon angioplasty for aortic recoarctation: results of Valvuloplasty and Angioplasty of Congenital Anomalies Registry.

Balloon angioplasty was performed in 200 patients with recoarctation of the aorta in a multicenter prospective study. The average age at the time of the procedure was 7.0 years (range 1 month to 26 years). Systolic pressure (mean +/- standard deviation) in the ascending aorta decreased from 134.5 +/- 23.4 to 127.4 +/- 22.0 mm Hg. The descending aortic systolic pressure rose from 92.7 +/- 18.2 to 114.1 +/- 21.6 mm Hg. Peak systolic pressure differences decreased from 41.9 +/- 19.6 to 13.3 +/- 12.1 mm Hg. The diameter of the recurrent coarctation site increased from 5.2 +/- 2.9 to 8.9 +/- 3.4 mm. After angioplasty residual pressure differences of less than or equal to 20 mm Hg were found in 79.4% of the patients. Five patients died of complications related to the procedure (2.5%). Two deaths were directly related to the technical aspects of the procedure and 3 patients died because of the severity of the underlying disease. One additional patient had a cerebrovascular accident. Femoral artery complications occurred in 17 patients (8.5%) and 8 patients required surgical thrombectomy. Balloon angioplasty offers a satisfactory alternative to surgery for recurrent coarctation; both results and complications compare favorably with surgical therapy.

Aortic Coarctation↗
PubMed1990

Clinical experience with fetal echocardiography.

Current ultrasound technology allows for accurate evaluation of the fetal heart. To evaluate the importance and accuracy of the routine clinical use of fetal echocardiography at our center, a consecutive series of 338 fetal cardiac studies of 323 patients was reviewed. Average gestational age was 24 weeks (range, 17 to 39 weeks). Forty-seven (15%) patients with abnormal conditions were detected. The most common indication for fetal cardiac scan was a family history of congenital heart disease (28%). Other indications were maternal diabetes mellitus (25%), fetal dysrhythmia (14%), other major defect (10%), drug exposure (10%), and obstetrician suspicion of fetal congenital heart disease on routine scan (10%). The highest yield of significant abnormal findings was among those referred for dysrhythmia (31%) and obstetrician suspicion of congenital heart disease (29%). Five fetuses with sustained supraventricular tachycardia and hydrops were successfully treated. The combination of fetal bradycardia and structural heart disease was the most ominous finding. Fifteen (4.6%) patients had clear changes in management based on the fetal echocardiogram. Our experience suggests that the routine use of fetal echocardiography is accurate and an important part of the overall management of the pregnancy considered at risk for producing an infant with congenital heart disease.

Diagnostic Errors↗
PubMed1989

Response of upper limb blood flow to handgrip exercise after Blalock-Taussig operation (for tetralogy of Fallot) or subclavian flap operation (for aortic isthmic coarctation).

To evaluate the effects of long-term reductions in perfusion pressure on blood flow responses to increased functional demand, 5 patients (aged 12 to 26 years) without normal aortic to subclavian artery blood flow to 1 arm as a result of surgery to treat congenital heart disease were studied. Five age- and sex-matched healthy (control) subjects were also studied. In the patients, forearm blood flow was not different in the surgical and normal arms at rest (3.6 +/- 0.6 vs 4.0 +/- 0.7 ml/min/100 ml, respectively, mean +/- standard error, difference not significant) despite lower systolic blood pressure in the surgical arm (87 +/- 2 vs 115 +/- 2 mm Hg, p less than 0.05). The increases in heart rate, systolic blood pressure, forearm electromyographic activity (index of muscle fatigue) and postexercise forearm blood flow (index of muscle oxygen deficit) were not different in response to 2.5 minutes of submaximal rhythmic handgrip exercise (50% of maximal force) performed with the surgical versus the normal arms. Peak forearm blood flow elicited by combined ischemia and maximal isometric handgrip exercise was not significantly different in surgical and normal arms in the group as a whole (39 +/- 4 vs 43 +/- 3 ml/min/100 ml, difference not significant), although some bilateral deficit (20 to 38%) was observed in 2 patients. No bilateral differences were observed in the control subjects under any condition. The finding of normal physiologic adjustments to submaximal rhythmic handgrip exercise with the surgical arm suggests that oxygen delivery during exercise was adequate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1988

Noninvasive assessment of hemodynamic responses to exercise in pulmonary regurgitation after operations to correct pulmonary outflow obstruction.

The influence of pulmonary regurgitation (PR) on exercise capacity is unknown. The hemodynamic responses to exercise in postoperative patients with PR was determined using Doppler-measured regurgitant fraction to indicate PR severity. Maximal heart rate, oxygen consumption and workload capacity were measured during upright cycle ergometry. Cardiac output was measured at rest and during submaximal supine cycle ergometry by pulsed Doppler echocardiography. Oxygen consumption was simultaneously measured and exercise factor was calculated as the change in cardiac output per change in oxygen consumption. Twenty-seven patients were compared with 17 age-, size- and sex-matched control subjects. Patients with PR had larger right ventricles (p less than or equal to 0.001), lower heart rate response (p less than or equal to 0.05), lower maximal oxygen consumption (p less than or equal to 0.005) and lower workloads (p less than or equal to 0.005) when compared with normal control subjects during maximal exercise testing. Exercise factor was the same for both groups. Patients with PR were then separated into mild, moderate and severe groups. Patients with mild PR had a normal response to exercise. However, patients with moderate and severe PR had lower maximal oxygen consumptions and maximal workloads than control subjects. Control, mild and moderate PR groups had similar exercise factors. Patients with severe PR had markedly low cardiac output responses. PR is associated with reduced exercise capability, which is related to the severity of the PR.

Adolescent↗
PubMed1988

Fetal cardiac Doppler flow studies in prenatal diagnosis of heart disease.

The prenatal diagnosis of fetal cardiac disease has become increasingly accurate as the technology of ultrasound has improved. Although two-dimensional real-time ultrasound remains the primary method of diagnosis, Doppler blood flow velocity estimates can provide valuable pathophysiologic information to support the anatomic diagnosis. We present six cases in which Doppler studies contributed to the accuracy of the diagnosis of fetal heart disease, including tetralogy of Fallot, right and left ventricular hypoplasia, atrioventricular canal defect, double-outlet right ventricle, and pulmonic stenosis. Velocities in these cases are compared with those in normal fetuses. If Doppler flow velocities are not consistent with the observed morphologic changes, further observations are indicated. Inasmuch as most anatomical heart lesions result in altered flow patterns, Doppler investigations of intracardiac and extracardiac flow should be a routine component of the fetal echocardiogram when structural abnormalities are found.

Adolescent↗