24 hour ambulatory blood pressure values corresponding to office blood pressure value of 130/80 mm Hg.

BACKGROUND: 24 hour ambulatory blood pressure monitoring (ABPM) values for patients who have office BP of 130/80 mm Hg have not been clearly reported. AIM: The determination of ABPM values in treated hypertensive subjects corresponding to a mean office BP of 130/80 mm Hg. METHODS: BP measurement in subjects 40-70 years old, by ABPM and mercury sphygmomanometer. The inclusion criteria were: mean office BP systolic (SBP) 128-132 mm Hg and diastolic (DBP) 78-82 mm Hg. Seventy six subjects met all study inclusion criteria. RESULTS: Mean office BP: SBP 129.5 ± 1.1 mm Hg, DBP 79.9 ± 1.3 mm Hg. Mean 24 hour BP: SBP 121.9 ± 2.0 mm Hg, DBP 73.1 ± 1.9 mm Hg. Mean awake BP: SBP 124.9 ± 2.4 mm Hg, DBP 75.5 ± 2.2 mm Hg. Mean asleep BP: SBP 109.1 ± 3.9 mm Hg, DBP 63.3 ± 4.0 mm Hg. CONCLUSIONS: The target values of ABPM identified in this study can be used in clinical practice and will contribute to risk stratification and treatment of hypertension.

Use of a novel transfer function to reduce repolarization interval hysteresis.

BACKGROUND: Cardiac repolarization is assessed by the QT interval on the surface electrocardiogram and varies with the heart rate. Standard QT corrections (QTc) do not account for the lag in QT change following a change in heart rate (QT hysteresis). Our group has developed and tested a transfer function (TRF) model to assess the effectiveness of a dynamic model of QT/RR coupling in eliminating hysteresis. METHODS: We studied three groups: group I, healthy volunteers (n = 23, 41 ± 17 years); group II, hypertensive patients (n = 25, 45 ± 11 years); and group III, patients in a predominately paced rhythm (n = 5, 75 ± 6 years). To vary the heart rate, either exercise bicycling in the supine position (groups I and II) or manipulation of the pacemaker parameters (group III) was done. We then compared a dynamic TRF model with a model based on weighted averages of previous RR intervals. Two parameters were tested: root mean square (RMS) of the error signal between measured and computed QT and the elimination of hysteretic loops. RESULTS: TRF-based measurements eliminated hysteresis in 22/23 (95%) group I patients, 21/25 (84%) group II patients, and 4/5 (80%) group III patients. When hysteresis elimination was not complete, the QT drift that followed RR intervals was different before and after bicycling (100 ms). In these patients, the corresponding QT interval did not significantly change during this period. The TRF model was found superior to the other tested models with respect to both analyzed parameters (RMS and hysteresis elimination). CONCLUSION: The TRF model limited QT hysteresis in healthy, hypertensive, and pacemaker-dependent patients. In addition, an important finding of QT drift in patients with hypertension was identified. With further study in these and other diseased states, the TRF model may improve our ability to measure accurately cardiac repolarization and to determine arrhythmia risk.

Effect of pomiferin administration on kidney ischaemia-reperfusion injury in rats.

The aim of the study was to analyse protective effects of different doses of pomiferin in therapy of reperfusion injury. Rats were randomly divided into five groups (n=10). One group was intact. Three medicated groups and one placebo group were subjected to ischaemia and reperfusion of the left kidney. Pomiferin was administrated by single gastric gavage in 2 ml of 0.5% Avicel solution in doses of 5, 10 and 20 mg/kg. The placebo group was given only Avicel solution. On day 15, all the animals were exsanguinated and the reperfused kidneys were recovered. Selected biochemical markers were assessed in blood: antioxidative enzymes, total antioxidative capacity, malondialdehyde, creatinine, urea and uric acid. Creatinine, urea and total proteins were analysed in urine and 24-hour diuresis was recorded. The kidney tissue samples were used for histopathological examination.The results confirmed the expected protective effects of pomiferin. Pomiferin supported defensive reactions of the body against free radicals (increased levels of superoxide dismutase, total antioxidative capacity), decreased lipid peroxidation (decreased malondialdehyde) and contributed to the recovery of kidney functions (creatinine and urea in blood). The best biochemical and histopathological results were achieved after pomiferin administration in the dose of 5 mg/kg.

The effect of short-term isometric muscle contraction and the Valsalva maneuver on systemic and pulmonary hemodynamics in patients with severe heart failure.

BACKGROUND: Chronic heart failure is characterized by high mortality, frequent hospitalization, and reduced quality of life. Patients with severe heart failure are often in very poor physical condition, they are unable to take part in the usual exercise programs, and therefore need an individual approach. HYPOTHESIS: To assess the systemic and pulmonary hemodynamic responses to maximum voluntary contraction of the lower extremity muscles (MVC-LEM) with persistent physiologic breathing, the Valsalva maneuver, and the combination of Valsalva with MVC-LEM. METHODS: Seventeen patients with severe heart failure (ejection fraction 20%) were exposed to 3 types of load for a period of 10 seconds: 1) MVC-LEM with persistent physiologic breathing, 2) the Valsalva maneuver, and 3) a combination of MVC-LEM with the Valsalva maneuver. During each measurement, a continuous, time-synchronized record was taken of the electrocardiogram, and the pulmonary and systemic blood pressures. RESULTS: There were slight changes in the heart rate and systemic blood pressure when comparing resting versus MVC-LEM values. There were much greater and significant changes (P < .01) in the systemic and pulmonary blood pressures when comparing resting versus the Valsalva maneuver or the combination of the MVC-LEM plus the Valsalva maneuver values. CONCLUSIONS: A short maximum voluntary contraction of the muscles of the lower extremities with persistent physiologic breathing did not have an abnormal effect on the systemic and pulmonary hemodynamics in patients with severe chronic heart failure. The Valsalva maneuver caused significantly higher hemodynamic changes in the systemic and pulmonary system with possible negative effects.

Changes in biomechanical parameters during heart perfusion and after midazolam pre-medication--experimental pilot study.

BACKGROUND: Midazolam is a frequently used benzodiazepine in anaesthesiology and intensive care. AIM: The aim of pilot study was to monitor its effect during heart perfusion in the laboratory rat. METHODS: The same groups of animals (n = 10). The 1(st) group was treated with midazolam in a dose of 0.5mg/kg i.p. The 2(nd) group was a placebo. After i.p. administration of heparine injection of 500 IU dose, the hearts were excised and perfused (modified Langendorf's method). Working schedule: stabilization/ischaemia/reperfusion proceed at intervals of 20/30/60 min. Monitored parameters in isolated heart: left ventricle pressure (LVP), end-diastolic pressure (LVEDP), contractility (+dP/dt(max)). RESULTS: The treated hearts showed improved postischemic recovery, reaching LVP values of 92 +/- 6 % at the end of the reperfusion, placebo only 61 +/- 7 %. In placebo hearts LVEDP rose from 10.0 +/- 0.5 mmHg to 43 +/- 4 mmHg after, in treated animals only about 25 mmHg. The treated hearts improved +dP/dt(max) recovery during reperfusion to 91 +/- 8 %. These values were significantly greater than those obtained from the placebo hearts. CONCLUSIONS: Positive changes in monitored parameters were found in this experimental pilot study. We conclude that the administration of midazolam in laboratory rats has a cardioprotective potential against ischemia-reperfusion induced injury.

Dynamic coupling between heart rate and ventricular repolarisation.

A novel model for the coupling between ventricular repolarisation and heart rate (QT/RR) is presented. It is based upon a transfer function (TRF) formalism that describes the static and dynamic properties of this coupling, i.e., the behaviour after a sudden change in heart rate. Different TRF models were analysed by comparing their capability to describe experimental data collected from 19 healthy volunteers using several RR stimulation protocols: (i) rest with deep breathing at 0.1 Hz; (ii) tilt with controlled breathing at 0.1 and 0.33 Hz; and (iii) cycling. A search for the best TRF led to unambiguous identification of a three-parameter model as the most suitable descriptor of QT/RR coupling. Compared with established static models (linear or power-law), our model predictions are substantially closer to the experimental results, with errors approximately 50% smaller. The shape of the frequency and step responses of the TRF presented is essentially the same for all subjects and protocols. Moreover, each TRF may be uniquely identified by three parameters obtained from the step response, which are believed to be of physiological relevance: (i) gain for slow RR variability; (ii) gain for fast RR variability; and (iii) time during which QT attains 90% of its steady-state value. The TRF successfully describes the behaviour of the RR control following an abrupt change in RR interval, and its parameters may offer a tool for detecting pharmacologically induced changes, particularly those leading to increased arrhythmogenic risk.

A comparison of the trough-to-peak ratio of cardio-selective beta-blockers in patients with newly diagnosed hypertension.

INTRODUCTION: The drug can be administered once a day, if the trough-to-peak ratio (T/P) exceeds 50-66%. The objective of this work was to determine and compare the T/P ratio for betaxolol hydrochloride and for extended-release metoprolol tartrate. METHODS: An open, randomized, prospective, comparative clinical study. The 24-h ambulatory blood pressure was measured with a SpaceLab 90207 automatic instrument (Redmond, Washington, USA) before and after 3 months of beta-blocker treatment. In order to determine the peak value, the individual maximum hourly mean blood pressure reduction was determined in the 3 to 6-h post-dose interval. For the determination of the trough value, the individual hourly mean blood pressure decrease in the 23-h post-dose interval, minimal 30 min after getting up in the morning was used. The T/P ratio was calculated as the mean of individual T/P ratios with statistical description of standard deviation (SD) and 95% confidence intervals (CIs). RESULTS: Betaxolol hydrochloride reduced the mean peak systolic blood pressure value by 17.87+/-8.32 mmHg, the mean peak diastolic blood pressure value by 16.07+/-6.65 mmHg, the mean trough systolic blood pressure value by 11.83+/-5.98 mmHg and the mean trough diastolic blood pressure value by 11.33+/-6.74 mmHg. The mean T/P ratio was calculated as 72.84+/-33.32% (95% CI, 60.40-85.285%) for systolic blood pressure and as 71.57+/-29.35% (95% CI, 60.62-82.53%) for diastolic blood pressure. Metoprolol reduced the mean peak systolic blood pressure value by 16.70+/-10.54 mmHg, the mean peak diastolic blood pressure value by 14.20+/-8.67 mmHg, the mean trough systolic blood pressure value by 11.30+/-9.12 mmHg and the mean trough diastolic blood pressure value by 10.00+/-8.38 mmHg. The mean T/P ratio was calculated as 70.59+/-31.66% (95% CI, 58.76-82.41%) for systolic blood pressure and as 66.95+/-31.60% (95% CI, 55.15-78.75%) for diastolic blood pressure. CONCLUSION: The T/P ratio determined for betaxolol hydrochloride and extended-release metoprolol tartrate is higher than 66%. This ratio guarantees a satisfactory 24-h effect of both the above-mentioned drugs.