Randomized trial of a hospital-based exercise training program after acute myocardial infarction: cardiac autonomic effects.

OBJECTIVES: This study sought to determine whether a moderate intensity supervised exercise training program, performed immediately after an uncomplicated acute myocardial infarction, improves recovery in cardiac autonomic function compared with standard advice about activity at home. BACKGROUND: Exercise training has beneficial effects on cardiac autonomic function and may improve prognosis after acute myocardial infarction. METHODS: Thirty-nine male and 10 female patients, mean (+/-SE) age 57 +/- 1 years, with an uncomplicated acute myocardial infarction were randomized to either a 6-week moderate intensity supervised hospital-based exercise training program (exercise group) or to an unsupervised low intensity home walking program (control group). Outcome measures included changes in baroreflex sensitivity (phenylephrine bolus method) and heart rate variability (24-h Holter monitoring) and the endurance time at 85% of peak oxygen consumption. RESULTS: At baseline, there were no significant differences in left ventricular ejection fraction (57 +/- 2% vs. 53 +/- 2%), frequency of anterior infarction (27% vs. 18%) and peak creatine kinase (1,256 +/- 170 vs. 2,599 +/- 295 IU) between the exercise and control groups. Baroreflex sensitivity (10.5 +/- 1.0 vs. 8.4 +/- 1.2 ms/mm Hg) and time domain measures of heart rate variability were also similar. After completion of the program, the exercise group exercised for a median of 15 min (interquartile range 12 to 25) at a workload of 104 +/- 7 W compared with 7 min (interquartile range 3.5 to 12) at a workload of 89 +/- 8 W in the control group (p < 0.01). There were significant (p < 0.001) improvements in baroreflex sensitivity and heart rate variability for the 49 patients combined but no differences between the exercise and control groups. Baroreflex sensitivity improved by 3.4 +/- 1.0 and 1.7 +/- 1.0 ms/mm Hg and the standard deviation of 24-h RR intervals by 36 +/- 6 and 40 +/- 10 ms, respectively (p > 0.1). CONCLUSIONS: A hospital-based exercise training program increased endurance capacity but did not improve recovery of cardiovascular antonomic function after uncomplicated acute myocardial infarction.

Noradrenaline and cardiac hypertrophy in the rat: changes in morphology, blood pressure and ventricular performance.

Noradrenaline hydrochloride (160 micrograms base/kg per h) or vehicle were infused subcutaneously for 11 days into 35 male Wistar-Furth rats using osmotic minipumps. Chronic noradrenaline infusion produced moderate hypertrophy of both ventricles without causing tissue oedema. Left ventricular (LV) hypertrophy was concentric with no change in cavity volume, increased mass: volume ratio (approximately 50%) and increased fibre diameter (approximately 25%). In the conscious rat, noradrenaline produced only a slight increase in mean arterial pressure (13%) and heart rate (11%) but a marked increase in the variability of mean blood pressure (250%). The extent of LV hypertrophy was not related to the level of mean blood pressure or to its variability. In the anaesthetized rat, peak cardiac pumping ability was normal before and after cardiac autonomic blockade. Peak pressure-generating ability during aortic occlusion was increased in hypertrophied hearts before autonomic blockade but was similar to control rats after autonomic blockade. Chronic noradrenaline administration produces cardiac hypertrophy which has many similarities to hypertensive cardiac hypertrophy but no clear association with the level of blood pressure.

Chart recorder paper minder.

Many paper based chart recorders still suffer from paper uptake systems for the collection of chart record that operate inefficiently or haphazardly. An efficient low cost paper minder using 1.2 mm diameter stainless steel wire for the Siemens-Elema AB Mingograph 7, has been developed. This wire pivots from the end of the chart viewing table and provides an effective force to redirect paper into the standard collecting basket over the entire range of paper speeds.