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Biomedical subjects

A R Leon

Publications and source records attributed to A R Leon.

15 recordsLinked to original sources
PubMed2004

Comparison of patient-controlled and operator-controlled conscious sedation for restorative dentistry.

BACKGROUND AND OBJECTIVE: The use of midazolam for conscious sedation is an accepted method of anxiety control in restorative dentistry. A lack of predictability in its effects requires the dose of midazolam to be adjusted to individual patient's requirements. We determined whether patient-controlled sedation was a suitable alternative to operator-controlled sedation in restorative dentistry. METHODS: A randomized crossover clinical trial involving 35 consecutive patients undergoing similar dental procedures. Patients were randomly given midazolam, administered either by the patient or by the operator at the first visit and the alternative option on the second visit. All patients were ASA I-II and their ages ranged between 20 and 48 yr. Blood pressure, heart rate, oxygen saturation and patient satisfaction were recorded. RESULTS: The onset time and initial dose for sedation were similar with the two methods of administration and the sedation scores and vital signs were satisfactory. In the patient-controlled group the mean total dose of midazolam was 7.9 (+/- 4.2 SD) mg cf. 4.2 (+/- 1.8 SD) mg in the operator-controlled group (P < 0.05). The time to fitness for discharge (15.4 (+/- 11.9 SD) min) was greater in the patient-controlled group cf. the operator-controlled group (8.5 (+/- 9.5 SD) min), P < 0.05. CONCLUSION: This study shows that patient-controlled sedation is a suitable alternative to operator-controlled sedation in the management of anxious dental patients.

Adjuvants, Anesthesia↗
PubMed2000

Bradyarrhythmias, temporary and permanent pacing.

Bradycardia is common in critical care units. It may be transient, asymptomatic and of little consequence, or life-threatening. Bradycardia may result from abnormalities of the sinus node, atrioventricular node, or the His-Purkinje system. It may also be precipitated by drug effects or enhanced vagal tone. Proper diagnosis is pivotal to determining prognosis and management. Temporary and permanent pacing is now readily available, markedly improving the morbidity and mortality associated with bradyarrhythmias.

Atrioventricular Node↗
PubMed1994

Catheter ablation of atrial flutter using radiofrequency energy.

Sixteen patients with type I atrial flutter underwent an attempt at radiofrequency catheter ablation (8 women, 8 men, mean age 53 +/- 11 years). The primary criterion used to identify sites for radiofrequency energy delivery was the identification of a fractionated electrogram. Radiofrequency energy was delivered for 20 to 30 seconds. Radiofrequency catheter ablation was acutely successful in 13 patients and unsuccessful in 3. During a mean follow-up of 10 +/- 4 months, 9 of 13 patients with a successful acute result (69%) remained free of recurrent atrial flutter or atrial fibrillation. The ability to induce nonclinical types of atrial flutter was associated with an unsuccessful outcome. A greater proportion of electrograms recorded at successful sites demonstrated electrogram stability compared with unsuccessful ablation sites. None of the electrograms recorded at successful ablation sites were fractionated or had a double potential. This study demonstrates that radiofrequency catheter ablation of type I atrial flutter can be achieved safely.

Adult↗
PubMed1993

Apparent change in cardiac geometry during single-photon emission tomography thallium-201 acquisition: a complex phenomenon.

We investigated the frequency and extent of changes in heart position and geometry independent of body motion during stress single-photon emission tomography (SPET) thallium-201 myocardial perfusion imaging. Following an exercise treadmill test, patients had a 22.1-min SPET acquisition which was followed immediately by a static image acquisition for 1 min with the camera position identical to the first view of the SPET study. Point sources were placed on the body to monitor patient motion. Cardiac motion was assessed by an approach which mimicked a cross-correlation technique applied to cardiac count profiles along the horizontal and vertical directions from the first view of the SPET study and the static image. A large percentage (87.5%) of cases had some degree of horizontal or vertical motion. Pixel shifts in cardiac position of > or = 2 pixels (12 mm) occurred in 60% of patients. In 37% of patients who moved the cardiac motion was consistent with simple translation of the heart and thus amenable to correction using proposed SPET motion-correction programs. The peak heart rate achieved during stress and the ratio of the heart rate immediately before SPET acquisition to the resting heart rate were determined to be independent predictors of patient motion during SPET acquisition. Cardiac motion changes were minimal at (13.3 +/- 2.2) min after cessation of exercise. The implications of these findings for the accuracy of SPET 201Tl require further investigation.

Algorithms↗
PubMed1993

Radiofrequency catheter ablation of right ventricular outflow tract tachycardia late after complete repair of tetralogy of Fallot using the pace mapping technique.

While surgical repair of tetralogy of Fallot has improved the long-term outlook for this patient population, sudden death late after repair remains a problem. Ventricular tachycardia (VT) originating in the right ventricular outflow tract (RVOT) is a well described, clinically important finding following surgical repair of tetralogy and a number of investigators suggest that this VT plays a critical role in the etiology of sudden death. We report two patients with RVOT VT late after repair of tetralogy who underwent successful radiofrequency ablation of their tachycardia.

Adolescent↗
PubMed1993

Inhomogeneity of gated and ungated SPECT technetium-99m-sestamibi bull's-eyes in normal dogs: comparison with thallium-201.

By computer simulation, we have previously hypothesized, independent of the isotope imaged, that differences in view-to-view resolution and attenuation patterns predictably cause count density distortions in SPECT images. We tested the simulation predictions for both ECG-gated and ungated SPECT 99mTc-sestamibi and SPECT 201Tl myocardial perfusion images in normal dogs. In agreement with the predictions of the computer model, distortions in SPECT 99mTc-sestamibi myocardial perfusion images are virtually equivalent to SPECT 201Tl, dependent on the exact SPECT acquisition orbit and markedly different for a posterior 180 degrees acquisition arc compared to an anterior 180 degrees acquisition arc. Furthermore, ungated and gated SPECT 99mTc-sestamibi images show similar count inhomogeneities. These results suggest that little is to be gained from a 360 degrees acquisition with SPECT 99mTc-sestamibi, and that image distortions from gated or ungated SPECT 99mTc images with 180 degrees orbits will be similar to those in SPECT 201Tl images.

Adenosine↗
PubMed1992

Comparison of single-photon emission computed tomographic (SPECT) myocardial perfusion imaging with thallium-201 and technetium-99m sestamibi in dogs.

OBJECTIVES: The purpose of the present study was to compare single-photon emission computed tomographic (SPECT) myocardial images of technetium-99m (Tc-99m) sestamibi and thallium-201 (Tl-201) isotopes in the same dog undergoing partial coronary occlusion during pharmacologic vasodilation. BACKGROUND: To date, no controlled study has been reported comparing SPECT Tc-99m sestamibi with SPECT Tl-201 imaging during stress with anatomic and physiologic standards. METHODS: Mongrel dogs were anesthetized with chloralose and instrumented to record left anterior descending coronary blood flow and aortic pressure. Partial coronary occlusion with a hydraulic cuff reduced coronary vascular conductance, which is equal to the coronary blood flow normalized to aortic pressure during peak vasodilation with intravenous adenosine. Each dog received 5 mCi of Tl-201, then 30 mCi of Tc-99m sestamibi during partial coronary occlusion at peak vasodilation. Tomographic myocardial imaging was performed in a 180 degrees anterior arc scan for 33.5 min, first with Tl-201, and later, without moving the dog, for 33.5 min with Tc-99m sestamibi. Postmortem staining defined the region underperfused because of its dependence on the artery that was partially occluded. RESULTS: In seven dogs with moderate reduction in coronary blood flow, coronary vascular conductance decreased with partial coronary occlusion (47 +/- 12%) during Tl-201 imaging and (47 +/- 8%, p = NS) during Tc-99m sestamibi imaging. The underperfused region was 23.9 +/- 6.4% of total left ventricular mass. Counts in the defects were 39% higher (0.86 +/- 0.08 of normal counts) for Tc-99m sestamibi than for Tl-201 (0.64 +/- 0.09 of normal counts, p < 0.001), and the defect on SPECT Tc-99m sestamibi images occupied only a fraction (0.37 +/- 0.30) of the area of the defect on the Tl-201 images of the same dog. Bull's-eye displays constructed from the pathologic slices showed that the Tl-201 defect size was closer to the underperfused region of the left ventricular mass determined pathologically than was the Tc-99m sestamibi defect size. In four additional dogs a severe, near total coronary occlusion was created during Tl-201 and Tc-99m sestamibi administration. In these dogs, similar defect contrast (0.55 +/- 0.12 vs. 0.62 +/- 0.09, p = NS) and areas (0.18 +/- 0.07 vs. 0.18 +/- 0.11, p = NS) were observed with Tl-201 and Tc-99m sestamibi, respectively. CONCLUSIONS: Tomographic myocardial imaging with Tc-99m sestamibi during moderately severe partial coronary occlusion underestimated the area of the defect relative to Tl-201 or to the pathologic reference standard in dogs. Defect contrast was sharper with tomographic myocardial Tl-201 than with tomographic myocardial Tc-99m sestamibi during moderately severe partial coronary occlusion.

Adenosine↗
PubMed1977

The periodontium and restorative procedures. A critical review.

The literature associated with the effect on the periodontal tissues of restorative procedures has been reviewed. Opinions have changed from the assumption that only poor restorative dental treatment led to periodontal disease, to the present concept, that even clinically sound restorations, if positioned subgingivally, may be important aetiological factors in the initiation of periodontal disease.

Adolescent↗