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Biomedical subjects

N Garvie

Publications and source records attributed to N Garvie.

11 recordsLinked to original sources
PubMed2005

Circulation time in man from lung to periphery as an indirect index of cardiac output.

Circulation time (Ct) between lung and periphery may be a surrogate for cardiac output, estimated here, for the most part, as the time between taking a breath of nitrogen and peripheral detection of a desaturation pulse. Use of pulse oximetry involves an internal, instrument delay; however, using the ear, we found shortening with exercise (12.1 +/- 0.37 sec, at rest; 9.1 +/- 0.25 sec at 100 watts), lengthening after beta-blockade, and lengthening in patients with echocardiographic and clinical left heart failure (8 patients 16.2 +/- 1.1 sec; 6 controls 12.0 +/- 0.5 sec). Pulse oximetry failed, however, to discriminate heart failure from normal in several patients. In patients referred to a department of nuclear medicine for assessment of chest pain, pulse oximetry (finger and ear) showed unacceptable variability. Nuclide delays between lung and carotid artery correlated significantly with the reciprocal of gated SPECT estimated cardiac output (Q(gs)); not so, however, for lung to finger. In normal subjects, an old Waters fast response oximeter gave short, reproducible Ct estimates and a significant correlation with the reciprocal of (indirect Fick) cardiac output (Q(if)). The relationship for normal subjects was: Ct = 0.28 x 60/Q(if) + 2.8 sec (Q(if) in L min.; P slope < .001).

Atenolol↗
PubMed2001

Scintigraphic assessment of colonic transit in women with slow-transit constipation arising de novo and following pelvic surgery or childbirth.

BACKGROUND: Colonic transit has not been compared between patients with slow-transit constipation (STC) arising de novo (idiopathic) and those whose symptoms followed pelvic surgery or childbirth (acquired). METHODS: In 48 women, with either idiopathic (n = 36) or acquired (n = 12) STC, 111In-radiolabelled diethylene-triamine penta-acetic acid colonic scintigraphy was performed to determine patterns of delay (generalized or left sided), the 'severity' of transit disturbance between subgroups, and the association with age or duration of symptoms. Results were compared with those in healthy women. Patterns of colonic transit disturbance were assessed using previously defined criteria. In those with a generalized delay, variables reflecting the overall rate of isotope progression throughout the colon were calculated: gradient of geometric centre of isotope progression and estimated evacuation time of the isotope. RESULTS: The pattern of transit delay was similar between the subgroups, but the 'severity' of the transit abnormality was significantly worse in those with chronic idiopathic symptoms. In the chronic idiopathic STC subgroup only, there was a significant correlation between both age and duration of symptoms and severity of transit disturbance. CONCLUSION: This study demonstrates that differences in colonic transit exist between subgroups of patients with STC. These might be explained by differences in duration of symptoms or differences in aetiology.

Adult↗
PubMed1997

Bone scintigraphic appearance of asymptomatic hydroxyapatite-coated hip arthroplasties.

To obtain information about the bone scintigraphic appearance of a hydroxyapatite (HA)-coated proximal femoral implant, this examination was performed on 24 patients with a clinically and radiologically successful femoral implant in hip arthroplasty. The prosthesis had a proximal HA coating for supplementary fixation. The patients' mean age was 50.3 years (range, 28-65 years) at operation. The interval from the operation to the scintigraphy ranged from 6 months to 5.5 years (mean, 2.2 years). Scintigraphy was performed using 99mTc-medronic acid. Quantitative counts were recorded in 4 zones: 3 along the length of the implant (trochanteric region with HA coating, midprosthesis, and distal tip) and 1 below the prosthesis. The results were expressed as ratios using the nonoperated femur as a control value. The results demonstrated that the mean activities in all 4 zones were increased relative to the untreated side. The highest activity was observed in the region around the prosthetic tip, with an elevation of 46% above the control value. This activity showed a significant decline over time. The counts recorded in the trochanteric region, where the implant was coated with HA, were 20% above the control value and similar to those seen in its adjacent noncoated midprosthetic region. In the trochanteric region, however, the activity did not show a decline over the follow-up period.

Adult↗
PubMed1987

Motor responses of the oesophagus to intraluminal distension in normal subjects and patients with oesophageal clearance disorders.

Oesophageal motor responses to intraluminal distension were studied manometrically in 16 healthy volunteers and in nine patients with disordered swallowing, who had prolonged oesophageal clearance without structural abnormality. In the normal subjects distension was associated with an increased number of secondary contractions above the balloon, decrease of all contractile activity below the balloon and was accompanied by an aborally propulsive force which occurred independently of the perception of discomfort. Cholinergic blockade abolished the proximal distension induced contractile response, but did not affect primary peristalsis. Despite normal sensory thresholds, proximal excitatory responses to distension were absent in six and distal inhibition was absent in seven patients. These results show that the normal human oesophagus responds to distension with a proximal enhancement of propulsive motor activity, mediated through a cholinergic pathway. This may be defective in some patients with disordered oesophageal transit. Investigation of the motor responses to intraluminal distension may thus be a useful adjunct to standard manometry for studying patients with suspected oesophageal clearance dysfunction and might allow identification of disordered enteric nervous control.

Adult↗
PubMed1982

Radionuclide ventriculography: a noninvasive method for the detection and quantification of left-to-right shunts in atrial septal defect.

The present investigation was undertaken to assess a new scintigraphic method for the diagnosis of left-to-right shunts due to atrial septal defect based on the differing stroke volumes of left and right ventricles and to compare it with oxymetric data. Radionuclide ventriculography was carried out after injection of 20 mCi 99mtechnetium-labeled red blood cells. Time-activity curves were obtained from the left and right ventricular regions, and the ratio (A) of end-diastolic-end-systolic count rate differences for the left and right ventricles was calculated. The left-to-right shunt (in percent of the pulmonary flow rate) is then given as 100 X (1 - A/1.43; 1.43 being the previously determined mean value of A in 66 normal patients. In 16 patients with an atrial septal defect and/or partial anomalous pulmonary venous connection a correlation of r = 0.81 was found between those shunts determined by the scintigraphic method and those calculated by oxymetric data. The specificity of the method and the sensitivity in detecting left-to-right shunts exceeding 30% are high. The method is practical and already widely used for determination of ejection fraction end-diastolic volume and other factors. The combination of this technique with other methods for shunt diagnosis such as gamma-fit analysis may prove of special value.

Heart↗
PubMed1979

A simple method for correcting left ventricular equilibrium radionuclide angiography for the effects of arrhythmias.

A simple method of correcting equilibrium radionuclide angiographic data for the effects of arrhythmias is proposed. This involves no further acquisition time or inconvenience to the patient. This correction is necessary in patients with marked arrhythmias as the left ventricular time-activity curve (LVTAC) becomes distorted with greater sampling time in the first few frames of the LVTAC than in later frames. This will show on the LVTAC as greater counts in the first few frames and will lead to an overestimation of left ventricular ejection fraction (LVEF) and wall motion. The method proposed normalises each frame to make the contribution from a non-cardiac region constant over the cardiac cycle. Results of the correction are presented and discussed.

Arrhythmias, Cardiac↗