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Biomedical subjects

A F Calvert

Publications and source records attributed to A F Calvert.

12 recordsLinked to original sources
PubMed1987

A matched pairs comparison of cycle ergometry and treadmill exercise testing in the evaluation of coronary heart disease.

In 105 patient pairs, matched for sex, aged within a ten-year range and with closely similar coronary disease, the sensitivity and specificity of treadmill testing using the Bruce Protocol was compared to cycle ergometry using the 100 kpm/min (16 W/min) increment protocol, and found to be similar. The parameters of use were ST segment depression (sensitivity of 52% for treadmill and 61% for cycle), test angina (65% and 61%), significant work impairment (66% and 68%) and impaired blood pressure response (31% and 20%). The sensitivity was increased (treadmill to 84%, cycle to 89%) if the four parameters were grouped, and abnormality in any one of them was regarded as a positive test. The equivalent severity of coronary disease resulted in more severe work impairment on the cycle than on the treadmill. The mean work level of the treadmill group was 80%, and of the cycle group, 61% of their respective, nomographically predicted, normal values. The difference was similar for the zero, single and multivessel disease groups. This difference should be recognised when comparing the two techniques.

Angina Pectoris↗
PubMed1984

True sensitivity of cardiac exercise testing. A combined clinical evaluation of multiple parameters.

Maximal exercise tests were performed in 308 patients with angiographically defined coronary disease, in 38 patients whose coronary vessels were not obstructed, and in 236 clinically normal volunteers. The sensitivity of parameters indicating ischaemia was evaluated singly and in combination in each group. The most sensitive individual parameters were work capacity restriction (65%), ST segment depression (56%) and test angina (55%). When the sequence of parameters were assessed successively in the coronary group, the sensitivity rose from 56% with ST depression to 70% with the addition of test angina, to 85% when work capacity restriction was added, and to 87% when inadequate heart rate or blood pressure responses or repetitive ventricular arrhythmias were included. In the group of patients whose coronary vessels were not obstructed, substantial clinical abnormalities and a bias to carry out angiography in those with abnormal exercise responses led to false ST segment changes in 34%, and, in a further 20%, to positivity in the other parameters. In clinically normal subjects a 15% "false" positive rate occurred. One parameter (R wave amplitude change) was falsely positive in 24%, and was therefore excluded. Grouped parameter sensitivity for patients who exercised on a bicycle and those who used a treadmill was similar.

Coronary Disease↗
PubMed1980

Hydroxyurea induced hepatitis.

A case of hydroxyurea-induced self-limited hepatitis with an influenza-like reaction to hydroxyurea therapy is presented. The association was supported by recurrence of the symptoms on rechallenge with the drug.

Chemical and Drug Induced Liver Injury↗
PubMed1980

Glucose-6-phosphate dehydrogenase in an Afro-American population.

6,366 Afro-American infants were screened for G6PD activity. 379 males (11.4%) and 77 females (2.5%) were deficient. Confirmation was made by a standard spectrophotometric assay. The results for the male infants in this study are comparable to those found in other studies which accurately establish the deficient male.

Black or African American↗
PubMed1975

Monitoring for serious arrhythmias and high risk of sudden death.

Ventricular premature beats (VPBs) are present in 85% of patients with coronary heart disease (CHD). A classification of VPBs based on frequency, multiformity, repetitive pattern, and degree of prematurity promises to aid in identifying patients at high risk of sudden death. Advanced grade or repetitive forms of VPBs are observed in 41% of patients with CHD who are monitored for 24 hours while ambulatory. Exercise stress is less effective than monitoring, but when advanced grades are exposed by exercise, they are likely to be persistent for two or more hours during monitoring. Such persistent and advanced grades characterize patients with multivessel coronary artery disease. Diurnal variations occur in VPB frequency and pattern with significant reduction during sleep. This as well as other facts suggest a primary role for neural activity in the genesis of ventricular ectopy. The relevance of these observations to sudden death is considered.

Aged↗