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Biomedical subjects

R D Okada

Publications and source records attributed to R D Okada.

At least 145 records · Page 8Linked to original sources
PubMed1981

Right Ventricular function in aortic and mitral valve disease.

Radionuclide ventriculography of the right heart was performed in 56 patients within two weeks of cardiac catheterization using a gated first-pass technique. Thirteen patient served as normal controls, and 43 patients had severe aortic or mitral valve disease or both, 35 of whom subsequently underwent valve surgery. Right ventricular ejection fraction (RVEF) and the presence of central venous reflux was determined and related to catheterization findings. In normal patients, RVEF was 60 plus or minus 7 percent (mean plus or minus 1 SD). In patients with valvular disease, the RVEF was below the normal range in only 2/14 (14 per cent) when right ventricular peak systolic pressures were less than 50 mm Hg, compared with 16/29 (55 percent) with an RVEF below normal when right ventricular peak systolic pressures greater than 50 mm Hg (P less than .05). In contrast, there was no relation of right ventricular ejection fraction to ventricular filling pressure in valvular heart disease patients. There was no difference in early postoperative course in patients with normal or reduced ejection fraction. Central venous systolic reflux was not presented in normal patients, but was present in 3/12 (25 percent) and 22/25 (88 percent); P less than 0.1) of patients with right ventricular systolic pressures below and above 55 mm Hg, respectively, including all ten patients with documented tricuspid regurgitation. Radionuclide assessment of right ventricular function in patients with aortic or mitral valve disease or both provides information that cannot be inferred from right-sided pressure measurements.

Adult↗
PubMed1981

The effect of pulsatile perfusion on preservation of left ventricular function after aortocoronary bypass grafting.

Pulsatile perfusion has been reported to be of value in intraoperative myocardial protection. To evaluate this technique, we studied 26 patients undergoing aortocoronary bypass grafting. Ejection fraction determinations from multigated cardiac blood pool scans, serial hemodynamic monitoring, and total CPK and MB-CPK sampling were performed early (4, 6 and 8 hours after bypass) and 10 days after operation. In 12 patients, pulsatile perfusion was started immediately after aortic cannulation and continued until 10 minutes after cessation of bypass; 14 patients had standard nonpulsatile perfusion. All patients had a single aortic cross-clamping and potassium cardioplegia. Cross-clamp time (46 +/- 3 and 46 +/- 3 minutes [+/- SEM]), total bypass time (94 +/- 4 and 89 +/- 6 minutes), and mean perfusion pressure (82 +/- 5 and 83 +/- 3 mm Hg) were comparable in the pulsatile and nonpulsatile groups, respectively, as were extent of coronary disease and number of bypass grafts. Preoperative and postoperative ejection fractions for pulsatile and nonpulsatile groups, respectively, were 0.57 +/- 0.03 and 0.55 +/- 0.04 before operation, 0.37 +/- 0.03 and 0.40 +/- 0.04 4 hours after bypass, 0.40 +/- 0.03 and 0.46 +/- 0.04 at 6 hours, 0.51 +/- 0.05 and 0.52 +/- 0.07 at 8 hours and 0.56 +/- 0.05 and 0.53 +/- 0.04) 10 days after operation. Mean arterial pressure, left atrial pressure and serial cardiac indexes were similar in both groups. There were no perioperative myocardial infarctions by ECG in either group. Total CPK (586 +/- 78 and 617 +/- 140 IU/l) and peak MB-CPK (73 +/0 14 and 61 +/- 11 IU/l) were comparable in the pulsatile and nonpulsatile groups, respectively. Pulsatile perfusion offers no advantage in myocardial preservation after aortocoronary bypass grafting in patients with normal left ventricular function.

Coronary Artery Bypass↗
PubMed1981

Pulmonary capillary wedge pressure, as inferred from lung areas in gated blood-pool scintigrams: concise communication.

To determine whether the apex-to-base distribution of pulmonary blood volume, as obtained from gated cardiac blood-pool scans, could be used as a noninvasive method to estimate mean pulmonary capillary wedge pressure (PCWP), gated blood-pool scans were analyzed in 77 patients who also had PCWP measurements at cardiac catheterization. Ten of these patients had gated cardiac blood-pool scans and PCWP measurements both at rest and during exercise. The apex-to-base distribution of pulmonary blood volume was determined from the end-systolic frame of the left anterior oblique view by placing equal-sized regions of interest over the apex and base of the right lung. The ratio of apex counts over base counts (A/B ratio) was considered abnormal if greater than unity. The mean A/B ratio was 1.15 +/- 0.27 (1 s.d.) for the 32 studies associated with an abnormal mean PCWP (greater than 12 mm Hg). The mean A/B ratio was 0.85 +/- 0.23 for the 55 studies associated with a normal mean PCWP (p less than 0.01 comparing normal group with abnormal). The sensitivity of the A/B ratio for a mean PCWP greater than 12 mm Hg was 81%R (26/32). The specificity of the A/B ratio for a mean PCWP greater than or equal to 12 mm Hg was 89% (49/55). Thus, noninvasive determination of the pulmonary apex-to-base ratio from gated cardiac blood-pool scans appears to differentiate subjects with normal and abnormal mean pulmonary capillary wedge pressures.

Adult↗
PubMed1980

Current status of radionuclide imaging in valvular heart disease.

In valvular heart disease, there is a different radionuclide angiographic pattern in each of three left-sided valve abnormalities: pressure overload (aortic stenosis), volume overload (aortic or mitral regurgitation) and inflow obstruction (mitral stenosis). In pressure overload, the left ventricle is usually normal in size or minimally dilated. The ejection fraction may be normal, increased or decreased. In volume overload, there is left ventricular dilatation with a normal or reduced ejection fraction at rest. Scans may be performed during exercise to unmask abnormalities of ventricular function not evident at rest. In inflow obstruction, left ventricular function is usually normal but may be depressed. Right ventricular function may be abnormal secondary to pulmonary hypertension. Radionuclide angiography in valvular heart disease evaluates the impact of the valve abnormality on cardiac chamber size and function, which is useful in managing the patient, in determining the prognosis and in evaluating the success of valve surgery. Thallium-2-1 imaging evaluates regional myocardial blood flow and cell integrity and can be used to assess associated coronary artery disease.

Aortic Valve Insufficiency↗
PubMed1980

Exercise radionuclide imaging approaches to coronary artery disease.

Exercise thallium-201 myocardial imaging and exercise radionuclide angiography are the two techniques of nuclear cardiology most widely used for the diagnosis of coronary artery disease. EAch of these tests provides information of diagnostic and functional value. The diagnostic accuracy and clinical utility of these two tests for the detection of coronary artery disease are compared. The strengths and weaknesses of each approach are discussed. A clinical approach to the detection and evaluation of coronary artery disease using these radionuclide exercise techniques is presented.

Blood Volume↗
PubMed1980

Scintigraphic assessment of false left ventricular aneurysms.

After myocardial infarction, patients may develop congestive heart failure, arrhythmias, or peripheral emboli due to true or false left ventricular aneurysms. False ventricular aneurysms differ from true aneurysms in that has been rupture of the left ventricular myocardium into the pericardium without rupture of the pericardial sac. The diagnosis of false aneurysm is particularly important because, in addition to the problems cited, there is a high incidence of rupture that may be prevented with surgical intervention. Four patients presenting with congestive heart failure and studied by gated cardiac blood pool scintigraphy were shown to have false left ventricular aneurysms and confirmed angiographically or surgically. Technetium-99m-gated cardiac blood pool scintiscans demonstrated discrete paraventricular chambers usually posterior in position with marrow necked connections to the left ventricle. Thallium-201 rest myocardial perfusion scintiscans performed in two of the four patients demonstrated a defect corresponding to the neck of the false aneurysm in one patient and a larger defect in the second patient with both a true and false aneurysm. It was concluded that combined gated cardiac blood pool scintigraphy and 201Tl myocardial scintigraphy provide a noninvasive method for diagnosing false left ventricular aneurysms.

Aged↗
PubMed1980

The bifocal diverging collimator: a means of simultaneous biplane imaging of the heart during equilibrium radionuclide ventriculography.

We have constructed a bifocal diverging collimator (BDC), capable of simultaneously recording two views of the heart 50 degrees apart on each half of a standard imaging field. In this study, simultaneous two-view blood-pool scans using the BDC were compared with the same two separate views obtained using an all-purpose parallel-hole collimator (PHC), assessing left-ventricular ejection fraction and regional wall motion in 20 patients undergoing contrast left ventriculography (CV). Ejection fraction by BDC correlated closely with PHC (r = 0.94) and with CV (r = 0.88). Regional wall motion was scored qualitatively on a five-point scale from 3 (normal) to--1 (dyskinesis) with an 88% agreement between BDC and PHC and PHC for segment scores. The percentages for agreement between BDC and CV, and between PHC and CV, were identical, 79%. A single blood-pool scan acquisition using a new BDC provides information about global and regional left-ventricular function in two planes, comparable with that of a PHC.

Coronary Disease↗
PubMed1979

Radionuclide-determined change in pulmonary blood volume with exercise. Improved sensitivity of multigated blood-pool scanning in detecting coronary-artery disease.

To assess the clinical usefulness of radionuclide-determined changes in pulmonary blood volume in patients with or without substantial coronary-artery disease, we determined the ratio of pulmonary blood volume at rest as compared with that during exercise. We used multigated blood-pool images obtained at rest and during supine exercise to determine the blood-volume ratio in patients subsequently undergoing coronary arteriography for evaluation of chest pain. Exercise tests were performed by use of a submaximal-workload protocol, although all tests were limited according to each patient's symptoms. The mean exercise/rest pulmonary-blood-volume ratios were lower for persons without coronary-artery disease (0.94 +/- 0.06 [S.D.], 10 patients) and for those with disease confined to the right coronary artery (0.99 +/- 0.12, five patients), as compared with all others with coronary-artery disease (1.14 +/- 0.15, 37 patients) (P less than 0.01). A pulmonary-blood-volume ratio equal to or greater than 1.06 had a sensitivity of 79 per cent. Patients with coronary-artery disease not confined to the right coronary artery usually show an increase in pulmonary blood volume during supine exercise. No such change occurs in persons without coronary-artery disease.

Adult↗
PubMed1979

Electrocardiographic axis deviation in Navajo and Apache indians.

It has been our clinical impression that the range of the mean frontal-plane electrocardiographic QRS axis was greater than might have been anticipated in healthy Navajo and Apache Indians. To determine whether this clinical impression was correct, electrocardiograms were obtained from 146 Navajo, 144 Apache, and 159 non-Navajo non-Apache schoolchildren with normal findings on cardiovascular examinations. A mean frontal-plane QRS axis between -1 degrees and -90 degrees was present in 19 percent of the Navajo, 12 percent of the Apache, and 2 percent of the control schoolchildren. A mean frontal-plane QRS axis between +91 degrees and +180 degrees was present in 18 percent of the Navajo, 19 percent of the Apache, and 5 percent of the control schoolchildren. There is a high incidence of electrocardiographic mean frontal-plane QRS axis deviation in healthy Navajo and Apache schoolchildren.

Adolescent↗
PubMed1978

Relationship between plasma concentration and dose of digoxin in patients with and without renal impairment.

The purpose of this study was to determine if there is a linear relationship between oral doses of digoxin and various measurements of steady-state digoxin plasma concentration and urinary excretion in patients with wide range of renal function. Ten patients (mean age 58 years) with creatinine clearances greater than 50 ml/min/1.73 m2 BSA (mean creatinine clearance 80 ml/min/1.73 m2 BSA) and nine patients mean age 61 years) with creatinine clearances less than 50 ml/min/1.73 m2 BSA (mean creatinine clearance 20 ml/min/1.73 m2 BSA) were given digoxin tablets orally at two or three different dose levels (dose range 0.0313--0.5 mg/day). After a dosing period equal to at least five half-lives, three to four consecutive daily digoxin plasma concentrations were determined. Plasma concentrations and urinary digoxin excretion were measured during one 24-hour dosing interval at each dose level. Digoxin plasma and urine concentrations were determined in triplicate using radioimmunoassay. Individual patient plots provided evidence of linearity for: digoxin 24-hour steady-state plasma concentration vs dose; digoxin 24-hour cumulative urinary excretion versus dose; and area under the digoxin plasma concentration-time curve during a 24-hour dosing interval vs dose. Absolute values for these various parameters indicated substantial interpatient variation probably due to patient differences in both digoxin absorption and digoxin total body clearance. These results indicate that there is a linear relationship between digoxin plasma concentration and dose in patients with normal and decreased renal function. This linearity is support for dose-independent pharmacokinetics of digoxin in man. We conclude from these data that a change in digoxin dose should result in a proportional change in digoxin plasma concentration over the dose range examined.

Administration, Oral↗