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Biomedical subjects

A F Rickards

Publications and source records attributed to A F Rickards.

13 recordsLinked to original sources
PubMed1992

Rate-responsive pacing using electrographic parameters as sensors.

The use of evoked QT-interval and ventricular depolarization gradient as sensors for rate-responsive pacing is described in this article. The QT interval has been used as a biosensor in implantable pacemakers since 1981, and recent refinements have improved the rate response characteristics and simplified the programming of this pacemaker. Recently, QT and activity sensing have been combined to produce a dual-sensor rate-responsive pacemaker that may offer advantages over single-sensor devices. The ventricular depolarization gradient has been incorporated into a closed-loop rate-responsive pacing system and is undergoing clinical evaluation.

Electrocardiography↗
PubMed1992

Outcome following incomplete revascularisation by coronary balloon angioplasty in patients with multivessel coronary artery disease.

When performing coronary angioplasty in patients with multivessel disease, there is an increasing trend to attempt balloon dilation of only ischaemia producing coronary stenoses (a strategy generally associated with incomplete revascularization) rather than attempting to dilate all anatomically significant stenoses (complete revascularization strategy). However the clinical efficacy of the former strategy has been questioned. To explore further this issue, we reviewed the records of 64 consecutive patients with multivessel coronary artery disease undergoing their first angioplasty at our centre in the 15 month period, October 1st 1987 to December 31st 1988. In 59 of these 64 patients, a strategy of incomplete revascularisation [attempted dilation of at least one stenosis > or = 70% but with one or more residual stenoses > or = 70% that were not attempted] was pursued. Of these 59 patients, 18 (31%) has three vessel coronary artery disease [stenoses > or = 70% in all three major coronary artery territories] and 19 (32%) had undergone previous coronary bypass surgery. In all 59 patients, prior to angioplasty, it was attempted to identify the ischaemia producing (so-called 'culprit') lesion(s). In the 59 patients, 66 culprit lesions in 63 vessels were identified. At angioplasty, in all patients, attempted dilation was confined to the culprit lesion(s). Clinical success (successful dilation of all attempted lesions without the occurrence of in-hospital myocardial infarction, death, or coronary bypass surgery) was achieved in 53 (90%) patients. At one year following successful angioplasty, no patient had died or suffered a myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1979

Hemodynamic effects of intravenous metoprolol.

The hemodynamic effects of the cardioselective beta adrenergic blocking agent metoprolol, at a dose of 0.1 mg/kg body weight administered intravenously, were studied in 10 patients undergoing routine cardiac catheterization. The beta adrenergic blocking effect of the drug was confirmed by a highly significant reduction (53 percent, P less than 0.001) in the mean heart rate response to a challenge with isoproterenol, and by a mean heart rate rssponse to a challenge with isoproterenol, and by a highly significant reduction (73 percent, P less than 0.001) in the isoproterenol-induced increase in the first derivative of left ventricular pressure (dP/dt). An intrinsic negative inotropic effect was shown by a 43 percent reduction (P less than 0.05) in the response of mean left ventricular dP/dt when the heart rate was fixed by atrial pacing alone. With the combination of atrial pacing and isoproterenol, metoprolol produced a 48 percent reduction (P less than 0.01) in the response of mean left ventricular dP/dt, resulting from both the intrinsic depressor effect and the beta adrenergic blocking effect on the rate-independent beta agonist activity of isoproterenol. There was no significant change in right atrial, femoral arterial or left ventricular end-diastolic pressure; analysis of left ventricular angiograms performed during atrial pacing before and after metoprolol revealed no significant effect on angiographic ejection fraction, pressure-volume loops or diastolic compliance. In two patients improvement in segmental wall motion was noted, and no deterioration was seen in any patient. Metoprolol is an effective cardioselective beta adrenergic blocking agent that, under these conditions, reduces catecholamine-induced increases in heart rate and left ventricular dP/dt without significant alteration in ejection fraction, preload or afterload.

Adult↗
PubMed1979

Isolated congenital absence of coronary sinus.

A case is reported in which contrast angiography showed complete absence of the coronary sinus, the cardiac veins draining separately into left and right atria. Normal systemic venous drainage was demonstrated by contrast cross-sectional echocardiographic methods and later confirmed by conventional angiographic injections. In addition, angiography showed a stenosis in the anomalous cardiac vein draining into left atrium accounting for the presence of a continuous murmur for which the patient was initially referred.

Angiocardiography↗
PubMed1978

[Hemodynamic comparison of Starr-Edwards, Lillehei-Kaster and homograft valves in the mitral position (author's transl)].

In 16 patients with Starr-Edwards (SE) disc valves, 10 patients with Lillehei-Kaster (LK) valves, and 4 patients with fresh aortic homografts (HG) in the mitral position the hemodynamic qualities of the valves were studied. All three valve types in general showed similar results, but they differed clearly as far as special parameters are concerned. So SE valves had the highest pressure gradients, HG valves the lowest, whereas LK valves were in between. The results of the study lead to the conclusion that tilting disc valves implanted in the mitral position are the best compromise, since they are always available and their hemodynamic response can be tolerated.

Angiocardiography↗
PubMed1976

Effect of isoprenaline and nitroglycerine on pressure time indices and coronary graft blood flow in man.

In five patients studied 1 to 3 d after coronary artery surgery isoprenaline and nitroglycerine have been used to alter the systolic (TTI) and diastolic (DPTI) pressure time indices. A close correlation with the predicted relationship between diastolic coronary graft flow and the DPTI/TTI ratio has been demonstrated during isoprenaline-induced tachycardia. Nitroglycerine reduced diastolic coronary graft resistance and increased the DPTI/TTI ratio, effects which are desirable for the relief of angina.

Adult↗
PubMed1975

Coronary arteriographic study of mild angina.

The results of coronary arteriography, exercise, and pacing stress testing in 50 young patients with mild angina are analysed. There was a significant correlation between the results of stress tests and the secerity of disease. There were, however, patients with severe disease and negative tests. Fifty-six per cent of patients had disease which potentially could have been surgically treated. It is concluded that coronary arteriography is indicated in these patients with mild symptoms.

Adult↗