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Biomedical subjects

N Houston

Publications and source records attributed to N Houston.

14 recordsLinked to original sources
PubMed2001

Quality improvement within Independent Practitioner Associations: lessons from New Zealand.

AIMS: To ascertain what quality improvement activities are being performed by associations of general practitioners (GPs) in New Zealand, to find out how they are supporting these activities, and learn about their experience of the process. METHOD: A cross sectional questionnaire study of 25 independent practitioner associations (IPAs) in New Zealand. RESULTS: All respondents (n=25) believed quality improvement was a responsibility of their organization, and for 48% it was their highest priority. All organizations carried out and supported a range of quality improvement activities. The major perceived barriers to quality improvement were negative attitudes and lack of time and money to support the process. Strategies to overcome these barriers included providing comparative data to staff in a peer group setting and providing financial incentives, management support and education. CONCLUSIONS: Considerable quality improvement activity is occurring in primary care in New Zealand. A variety of barriers to the process and methods of overcoming them have been identified by some, but not all IPAs.

Attitude of Health Personnel↗
PubMed1984

Changes in rest and exercise myocardial perfusion and left ventricular function 3 to 26 weeks after clinically uncomplicated acute myocardial infarction: effects of exercise training.

The effects of exercise training on exercise myocardial perfusion and left ventricular (LV) function in the first 6 months after clinically uncomplicated acute myocardial infarction (AMI) were assessed in 53 consecutive men aged 55 +/- 9 years. Symptom-limited treadmill exercise with thallium myocardial perfusion scintigraphy and symptom-limited upright bicycle ergometry with equilibrium gated radionuclide ventriculography were performed 3, 11 and 26 weeks after AMI by 23 men randomized to training and 30 randomized to no training. Peak cycle capacity increased in both groups between 3 and 26 weeks (p less than 0.01), but reached higher levels in trained than in untrained patients (803 +/- 149 vs 648 +/- 182 kg-m/min, p less than 0.01). Reversible thallium perfusion defects were significantly more frequent at 3 than at 26 weeks: 59% and 36% of patients, respectively (p less than 0.05), without significant inter-group differences. Values of LV ejection fraction at rest, submaximal and peak exercise did not change significantly in either group. The increase in functional capacity, i.e., peak treadmill or bicycle workload, that occurred 3 to 26 weeks after infarction was significantly correlated with the increase in peak exercise heart rate (p less than 0.001), but not with changes in myocardial perfusion or LV function determined by radionuclide techniques. Changes in myocardial perfusion or LV function do not appear to account for the improvement in peak functional capacity that occurs within the first 6 months after clinically uncomplicated AMI.

Coronary Circulation↗
PubMed1982

The effect of a standardized psychological stressor on the cardiovascular response to physical effort soon after uncomplicated myocardial infarction.

To determine whether a standardized psychological stressor combined with physical stress might disclose ischemic abnormalities not evident with physical stress alone, 30 men, mean age 54, were evaluated seven weeks after clinically uncomplicated myocardial infarction. In the first 20 patients, two symptom-limited treadmill tests (TM) were performed on the same day, with and without superimposed psychological quiz (Q). In the next 10 consecutive patients, the Q was administered at a submaximal level (4 METs). When TM and TM + Q responses were compared, no significant differences were noted in the maximal levels of heart rate (HR), systolic blood pressure (SBP), rate pressure product, or in the prevalence of ischemic ST segment depression or angina pectoris. The HR and double product at which ischemic ST segment depression and angina pectoris appeared were similar for the two types of testing. The psychological stress of a psychological quiz may not, of course, approximate the effect of the more severe stressors individuals may encounter in their daily routines.

Arrhythmias, Cardiac↗
PubMed1982

Comparison of cardiovascular response to combined static-dynamic effort, postprandial dynamic effort and dynamic effort alone in patients with chronic ischemic heart disease.

The cardiovascular responses to combined static-dynamic effort, postprandial dynamic effort and dynamic effort alone were evaluated by upright bicycle ergometry during equilibrium-gated blood pool scintigraphy in 24 men, mean age 59 +/- 8 years, with chronic ischemic heart disease. Combined static-dynamic effort and the postprandial state elicited a peak cardiovascular response similar to that of dynamic effort alone; work load 643 +/- 156 and 638 +/- 161 vs 650 +/- 153 kg-m/min, respectively; heart rate 147 +/- 14 and 145 +/- 14 vs 143 +/- 17 beats/min; systolic pressure 195 +/- 26 and 200 +/- 25 vs 197 +/- 25 mm Hg; and rate-pressure product 286 +/- 48 and 292 +/- 55 vs 282 +/- 52. Heart rate, intraarterial systolic and diastolic pressures, rate-pressure product and ejection fraction were similar for the three test conditions at the onset of ischemia and at peak effort. The prevalence and extent of exercise-induced ischemic left ventricular dysfunction, ST-segment depression, angina pectoris and ventricular ectopic activity were also similar during the three test conditions. Direct and indirect measurements of systolic and diastolic blood pressure were highly correlated. The onset of ischemic ST-segment depression and angina pectoris correlated as strongly with heart rate alone as with the rate-pressure product during all three test conditions. The cardiovascular response to combined static-dynamic effort and to postprandial dynamic effort becomes more similar to that of dynamic effort alone as dynamic effort reaches a symptom limit. If significant ischemic and arrhythmic abnormalities are absent during symptom-limited dynamic exercise testing, they are unlikely to appear during combined static-dynamic or postprandial dynamic effort. This simplifies, the task of formulating guidelines for physical effort in patients with chronic ischemic heart disease, especially in providing "clearance" to perform avocational and vocational tasks involving combined static-dynamic and postprandial dynamic effort.

Aged↗
PubMed1980

A new method for evaluating antiarrhythmic drug efficacy.

To develop standards for distinguishing antiarrhythmic drug effect from spontaneous variability of premature ventricular complexes (PVCs), 21 males (mean age 56 +/- 8 years) with chronic ischemic heart disease and PVCs underwent symptom-limited treadmill exercise testing and 24-hour ambulatory monitoring before and after 2 weeks of placebo medication. Linear regression analysis was used to describe the relationship between baseline and placebo PVC frequency for various indexes of ventricular ectopic activity and to establish 95% and 99% one-tailed confidence intervals for this relationship within the group of 21 patients. The lower limit of baseline PVC frequency for which the procedure could distinguish a placebo from a true drug response, termed the "sensitivity threshold," was an average frequency of 2.2 PVCs/hour for ambulatory electrocardiographic monitoring and 1.2 PVCs/min for treadmill exercise testing. All patients exceeded the sensitivity threshold on baseline ambulatory ECGs, but only 38% of patients did so on baseline treadmill exercise tests. To establish antiarrhythmic efficacy with 95% confidence, the minimal percent reduction of PVCs between baseline and placebo visits was 68% for treadmill exercise testing and 65% for ambulatory electrocardiography. Although these standards were developed in patients with chronic ischemic heart disease, the model can be used to establish antiarrhythmic drug efficacy in any patient group.

Ambulatory Care↗
PubMed1979

Comparison of cardiovascular responses to static-dynamic effort and dynamic effort alone in patients with chronic ischemic heart disease.

Thirty men, mean age 55 years, known to have treadmill-induced ischemic ST-segment depression, performed static and dynamic effort, i.e., forearm lifting and treadmill exercise, separately and combined. Static effort was sustained at 20%, 25% or 30% of maximal forearm lifting capacity. Two symptom-limited treadmill tests, one with and one without added static effort, were performed on each of two visits. Compared with dynamic effort alone, combined static-dynamic effort decreased treadmill work load and increased heart rate, systolic blood pressure and rate-pressure product at the onset of ischemic ST-segment depression or angina pectoris: 7.1 +/- 0.4 vs 8.0 +/- 0.5 (SEM) multiples of resting oxygen consumption (mets), estimated; 141 +/- 3 vs 134 +/- 3 beats/min; 170 +/- 4 vs. 162 +/- 4 mm Hg and 239 +/- 8 vs 218 +/- 9 (p less than 0.001). The prevalence of angina pectoris was significantly less with combined static-dynamic effort than with dynamic effort alone. Static effort causes a resetting of the threshold at which ischemic abnormalities appear during dynamic effort.

Angina Pectoris↗
PubMed1979

A comparison of static and dynamic exercise soon after myocardial infarction.

The cardiovascular response to treadmill exercise testing and to isometric handgrip was compared in 20 selected patients three to five weeks after acute myocardial infarction. The heart rate and the heart rate-systolic blood pressure product were significantly higher during treadmill exercise than during two minutes of isometric handgrip sustained at 25% of maximum voluntary contraction. No significant difference in systolic blood pressure was noted between the two types of exercise while diastolic blood pressure was higher during isometric exercise. Asymptomatic ST-segment depression was noted in two patients during the the treadmill test and was absent during handgrip. Angina pectoris was not noted during either type of exercise. Ventricular ectopic activity was slightly more frequent during treadmill exercise. Isometric handgrip at 25% of maximum voluntary contraction may be performed safely soon after myocardial infarction and provides useful guidelines for performing many customary physical activities requiring upper extremity isometric exertion during early convalescence.

Blood Pressure↗
PubMed1978

Cardiovascular responses to dynamic and static effort soon after myocardial infarction. Application to occupational work assessment.

Static and dynamic work involving the arms and the legs was performed by 40 men seven weeks after myocardial infarction. Leg ergometry produced a significantly higher peak work load, systolic blood pressure (BPs), heart rate (HR), and HR X BPs X 10(-2) product (DP) than did arm ergometry: 842 +/- 178 vs 546 +/- 135 kg-m/min, 176 +/- 24 vs 154 +/- 19 mm Hg and 256 +/- 54 vs 219 +/- 48 (SD). Peak heart rates were 145 and 142. Endpoints were primarily muscular and generalized fatigue and dyspnea. Ischemic abnormalities and ventricular ectopy were more frequent with leg ergometry. Sustained forearm lifting elicited higher HR, PBs and DP responses than sustained handgrip contraction: 95 +/- 16 vs 91 +/- 16 beats/min, 162 +/- 18 vs 152 +/- 17 mm Hg and 154 +/- 33 vs 139 +/- 33 (SD). Ischemic ST segment depression and significant ventricuar arrhythmias were infrequent with static effort. Dynamic leg testing is superior to dynamic or static arm testing in assessing the capacity of patients to perform physical work tasks after myocardial infarction.

Adult↗
PubMed1977

Exercise testing soon after myocardial infarction.

Forty-six men under age 70, without clinical congestive heart failure or unstable angina pectoris, performed treadmill tests 3, 5, 7, 9 and 11 weeks after myocardial infarction. Patients were more frequently able to perform moderate exertion (2 mph, 14% grade) at 7 and 11 weeks than at 3 weeks following infarction. Ischemic ST-segment depression, usually unaccompained by angina pectoris, occurred in 45% of patients and was associated with a significantly increased incidence of subsequent coronary events. The presence of exercise-induced ventricular ectopic activity provided little independent prognostic information. No serious complications occurred in 210 tests. Exercise testing soon after myocardial infarction provides objective information concerning the capacity to resume physical activity, including return to work. Two tests, at 3-5 weeks and at 7-11 weeks, appear to provide most of the information contined in five tests performed during this time.

Aged↗