Emanuela Mutti

Spectral and sequence analysis of finger blood pressure variability. Comparison with analysis of intra-arterial recordings.

The aim of our study was to assess whether the Finapres device is able to accurately monitor not only average blood pressure values but also blood pressure variability. To examine this issue, we analyzed 30-minute recordings of finger and intra-arterial pressure simultaneously obtained at rest in 14 patients. We compared systolic blood pressure, diastolic blood pressure, mean arterial pressure, pulse interval (the reciprocal of heart rate), overall variability (standard deviation), and specific time-domain and frequency-domain components. Systolic blood pressure, diastolic blood pressure, mean arterial pressure, and pulse interval spectral powers were computed by fast Fourier transform over three frequency bands: low frequency (0.025 to 0.07 Hz), midfrequency (0.07 to 0.14 Hz), and high frequency (0.14 to 0.35 Hz). The coherence, ie, the degree of association between blood pressure and pulse interval powers obtained by the two techniques, was also assessed. Standard deviations of diastolic blood pressure, mean arterial pressure, and pulse interval were similar when assessed from the two recordings, whereas standard deviation of systolic blood pressure was overestimated by analysis of finger pressure recordings. All powers of diastolic blood pressure and mean arterial pressure and high-frequency powers of systolic blood pressure estimated from analysis of finger blood pressure tracings were superimposable to those obtained by analyzing invasive recordings. Low-frequency and midfrequency powers of intra-arterial systolic blood pressure were significantly overestimated by the analysis of finger blood pressure tracings (+13.7 +/- 4.4 mm Hg2, P < .01, and +2.3 +/- 0.9 mm Hg2, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

REPRODUCIBILITY OF NON-INVASIVE AND INTRA-ARTERIAL BLOOD PRESSURE MONITORING : IMPLICATIONS FOR STUDIES ON ANTIHYPERTENSIVE TREATMENT

Ambulatory blood pressure has been shown to be more reproducible than office blood pressure and thus to be more suited for studying the efficacy of antihypertensive drugs. In 34 untreated essential hypertensive subjects, we measured office and 24-h non-invasive or intra-arterial blood pressure twice over a 4-week interval; 24-h intra-arterial blood pressure was obtained by the Oxford method whereas 24-h non-invasive blood pressure was obtained by the automatic SpaceLabs 5300 device, with a 10 min (daytime) or 20 min (night-time) interval between measurements. The standard deviation of the mean difference (s.d.d.) between blood pressures obtained in each recording was taken as the reciprocal of blood pressure reproducibility. The s.d.d. was highest for office blood pressure and for single blood pressure readings taken from 24-h non-invasive recordings. The s.d.d. fell when the two 24-h average non-invasive blood pressures were considered. The fall was progressively greater as the number of ambulatory readings on which the average was calculated increased from two to 24, no further fall being observed when more than 24 values were considered. The maximal reduction in s.d.d. was 59% (systolic) and 42% (diastolic) as compared with the office s.d.d. The two 24-h mean values obtained by the intra-arterial approach were slightly more closely correlated than those obtained non-invasively. However, at comparable sampling rates, the s.d.d. was not substantially lower with 24-h intra-arterial blood pressure and including in the calculation the average of the thousand readings provided by this approach did not cause any further improvement.(ABSTRACT TRUNCATED AT 250 WORDS)

Limited reproducibility of hourly blood pressure values obtained by ambulatory blood pressure monitoring : implications for studies on antihypertensive drugs

Objective: To assess the reproducibility of average hourly blood pressure values obtained by 24‐h non‐invasive ambulatory monitoring. Patients: Fifteen outpatients with essential hypertension. In all subjects antihypertensive treatment was withdrawn for 4 weeks before and during the 4 weeks of the study. Methods: The 24‐h blood pressure was monitored by a SpaceLabs 5300 device (four readings per hour during the day and three readings per hour during the night) twice, at a 4‐week interval. Systolic (SBP) and diastolic blood pressure (DBP) were averaged for each hour and for the whole 24‐h period, and hourly and 24‐h reproducibility was quantified by the standard deviation of the mean difference (SDD) between the values obtained in the two recordings. Results: The SDD of hourly SBP and DBP was much greater than that of the 24‐h values and ranged widely between the hours of recording. The SDD of hourly SBP and DBP were also variably greater than the SDD of the 24‐h value in another 14 untreated essential hypertensives in whom 24‐h ambulatory blood pressure was monitored intra‐arterially twice at a 4‐week interval to calculate hourly average blood pressure on thousands rather than on three or four values per hour. Conclusion: Reproducibility is less for hourly than for 24‐h average blood pressure. This feature (which probably depends on behavioural differences between two recordings) suggests that ambulatory blood pressure measurement partly loses its advantages for reproducibility and reduction in trial size if the results are analysed over hourly periods.

EFFECT OF PLACEBO ON 24-H NON-INVASIVE AMBULATORY BLOOD PRESSURE

Twenty-four-hour mean ambulatory blood pressure has been shown to be devoid of a placebo effect. However, whether this is the case for different periods within the 24 h has not been established. In 27 essential hypertensive outpatients, blood pressure was measured in the doctors office and by 24-h ambulatory blood pressure monitoring after a 3-week wash-out period from antihypertensive treatment (Control) and following 4 weeks of placebo administration. Office systolic and diastolic blood pressures were reduced by placebo (-9.6 +/- 2.6 and -3.1 +/- 1.7 mmHg, P less than 0.01, respectively), whereas 24-h mean blood pressure values did not show any significant change. This was not the case for all 24-h subperiods, however, because during the initial 8h, systolic and diastolic blood pressures were slightly (-4.1 +/- 9.2 and -2.5 +/- 6.4 mmHg) but significantly (P less than 0.05) lower during placebo than during control. Similar findings were obtained in 14 additional essential hypertensive patients in whom neither placebo nor any other treatment was employed between the two office and 24-h blood pressure measurements. Thus, placebo treatment is associated with a blood pressure reduction in the initial portion of the ambulatory blood pressure profile, probably because of an attenuation of an initial transient alerting response to the procedure. Although so small as to leave the 24-h blood pressure mean unaffected, this may lead to some overestimation of the antihypertensive effect of treatment during an appreciable portion of the circadian blood pressure tracing.

Cardiovascular effects of smoking

Coronary heart disease (CHD) increases with smoking and this factor interacts with hypercholesterolemia and hypertension in raising the incidence of this condition in a greater than linear fashion. This can be explained by the adverse effect of smoking on plasma fibrogen, platelet turnover and lipid profile. It may also be accounted for, however, by the acute bradycardia, increase in blood pressure and generalized vasoconstriction accompanying smoking, due to a nicotine-dependent activation of the sympathetic nervous system. These effects (which in heavy smokers can raise blood pressure permanently) are only partly offset by beta-blockers and can only be abolished by opposing the cardiac and vascular sympathetic influences by alpha and beta-blockade combined.

Changes in 24 Hour Blood Pressure and in Cardiac and Vascular Structure in Normotensive Subjects with Parental Hypertension

Subjects with family history of hypertension represent a suitable model to investigate the mechanisms responsible for early cardiovascular structural and functional changes occurring in essential hypertension. In our study we have addressed the factors involved in determining the mild elevation in office blood pressure frequently observed in normotensive subjects with hypertensive parents. In 15 normotensive subjects with both parents hypertensive (FH++) and in 15 normotensive subjects with one parent hypertensive (FH(+)-) we found no evidence of a hyperreactivity to stress as compared to the responses of 15 normotensive subjects with no parental hypertension (FH--). On the contrary FH++ subjects were characterized by a significant although mild increase in their blood pressure values recorded either at rest and in ambulatory conditions over the 24 hours, including night sleep. FH++ and FH(+)- subjects also showed a greater left ventricular mass thickness and a greater minimal forearm vascular resistance than FH-- subjects. Thus, the elevation in blood pressure found in the pre-hypertensive stage in subjects with positive family history for hypertension does not reflect a hyperreactivity to the stress associated with physicians visit but indicates an early and persistent blood pressure elevation. This blood pressure elevation is accompanied by early cardiovascular structural changes which may indicate that these subjects are exposed to a higher risk even before developing overt hypertension.

Lack of effect of percutaneous transluminal renal angioplasty on nocturnal hypotension in renovascular hypertensive patients

Objective To investigate whether nocturnal blood pressure fall is blunted in renovascular hypertension and can therefore be used as a diagnostic criterion for this condition. Methods In 14 renovascular hypertensive patients (age 43.8±2.1 years, mean±SEM, clinic blood pressure 173.6±3.7mmHg systolic and 109.0±2.0mmHg diastolic) and in 14 age- and blood pressure-matched essential hypertensive controls 24 h ambulatory blood pressure was measured after washout from drug treatment, during angiotensin converting enzyme inhibitor treatment and, in renovascular hypertension, also after percutaneous transluminal renal angioplasty. Results The 24 h average systolic and diastolic blood pressures were 146.4±5.7 and 97.5±3.6mmHg in renovascular and 144.3±1.2 and 98.0±2.2mmHg in essential hypertensive patients. The angiotensin converting enzyme inhibitor treatment reduced 24 h average systolic and diastolic blood pressures by 8.5% and 9.7% in the renovascular and by 8.3% and 10.8% in the essential hypertensive group. Greater systolic and diastolic blood pressure reductions (-18.2% and −18.1%) were observed in renovascular hypertensive patients after percutaneous transluminal renal angioplasty. Blood pressure fell by about 10% during the night and the fall was similar in renovascular and in essential hypertensive patients. In the former group, nocturnal hypotension was similar after washout, during angiotensin converting enzyme inhibitor treatment and after percutaneous transluminal renal angioplasty. Similar results were obtained for nocturnal bradycardla. Conclusions Nocturnal blood pressure fall is equally manifest in renovascular and essential hypertension. The removal of the renal artery stenosis and blood pressure normalization do not enhance this phenomenon. Nocturnal hypotension seems therefore to be unaffected by renovascular hypertension.

Early twenty-four-hour blood pressure elevation in subjects with parental hypertension.

We studied 15 normotensive offspring of hypertensive parents, comparing them with 15 normotensive controls matched for sex, body mass index and age. In the offspring, both parents were hypertensive, while in the controls, neither parent was hypertensive. Blood pressure was measured at rest, during a variety of laboratory stressors (mental arithmetic, mirror drawing test, hand grip and cold pressor test), and was also monitored for 24 h in ambulatory conditions (Spacelabs 5300 M, Richmond, Washington, USA). Resting mean and diastolic blood pressures were higher (P less than 0.05) in the subjects with parental hypertension than in those without. The mean blood pressure rise induced by the laboratory stressors was not significantly greater at any time in the subjects with hypertensive parents compared with controls. Twenty-four-hour systolic and mean blood pressures, however, were significantly higher (P less than 0.05) in the subjects with hypertensive parents than in the controls. Thus the higher office blood pressure shown in the prehypertensive stage by subjects with parental hypertension is not due to hypersensitivity to stress, but represents an early and permanent blood pressure elevation.

Clinical and hemodynamic effects of celiprolol in essential hypertension.

The antihypertensive effect of celiprolol, a selective beta-adrenoceptor blocker with ancillary partial beta 2-agonist, vasodilator, and bronchosparing properties, has been evaluated in open and placebo-controlled trials. Celiprolol (200-600 mg once daily) has been reported to reduce blood pressure significantly in 60-80% of patients with side effects which are mild and low in frequency. The antihypertensive efficacy of celiprolol has been found comparable with that of propranolol, atenolol, metoprolol and nadolol, but celiprolol does not cause the same degree of bradycardia as these other drugs. By means of ambulatory blood pressure monitoring we have demonstrated that celiprolol, administered to 10 essential hypertensive patients (aged 20-64 years) as a single daily dose (200-400 mg), can induce a significant and sustained reduction in 24-h systolic and diastolic blood pressure, with no effects on 24-h heart rate. Similar results have been obtained in elderly patients (aged 65-74 years) responsive to this drug. Both in young and elderly patients treatment was well tolerated. Available evidence therefore suggests that celiprolol is an effective and safe antihypertensive drug, the favorable ancillary properties of which are likely to make its administration feasible in a broad range of patients.