Clinical and functional correlates of platelet cyclic GMP in essential hypertensives.

BACKGROUND: Platelets play a central role in atherothrombosis, which is responsible of major cardiovascular complications in human hypertension. Nitric oxide (NO) inhibits platelet aggregation via the second messenger cyclic guanosine monophosphate (cGMP). In essential hypertensives (EHs), we examined the relationship between platelet cGMP and clinical, hemodynamic, humoral variables as well as the responses to aggregating agents. METHODS: In untreated EHs (male/female 106/43, age 44.4 +/- 1.1 years, smokers yes/no 38/111), blood pressure (BP), heart rate (HR), and stroke volume (SV) (impedance cardiography) were assessed after supine rest and venous blood was sampled for platelet cGMP (radioimmunoassay on acid extracts of washed platelets), plasma cGMP, atrial natriuretic peptide (ANP), renin activity, aldosterone and platelet aggregation to epinephrine (EPI, 5 micromol/l), and adenosine diphosphate (ADP) (4 micromol/l) (optical aggregometry on platelet-rich plasma (PRP)). RESULTS: Platelet cGMP (7.0 +/- 0.3 pmol/10(9) cells, mean +/- s.e.m.) was lower in males and smokers than in their counterparts (P < 0.01 for both). Among the variables tested, platelet cGMP was related to number of cigarettes (-0.21), high-density lipoprotein cholesterol (HDLc) (r = 0.32), aldosterone (r = -0.21), and hemoglobin (-0.16); in a multivariate analysis that also included sex, HDLc was the best predictor of platelet cGMP. The aggregating response to EPI (r = -0.28), but not to ADP (r = -0.07, ns), was inversely related to platelet cGMP levels. CONCLUSIONS: cGMP in resting platelets of EHs is positively predicted by HDLc and is inversely related to the aggregating response to EPI. It is suggested that a defect of the platelet NO/cGMP system could identify uncomplicated EHs at higher risk of thrombotic events during surges of sympathetic activity.

How long shall the patient rest before clinic blood pressure measurement?

BACKGROUND: The optimal time at rest before clinic blood pressure (BP) measurement is still undefined. In this study in patients with essential hypertension, the time course of the hemodynamic changes during a 16-min rest in the chair-seated position was evaluated and compared with that observed in a stabilized postural condition, such as after a prolonged supine rest. METHODS: In 55 untreated essential hypertensive patients, BP, heart rate, stroke volume (impedance cardiography), and systemic vascular resistances were measured every other minute during a 16-min rest in the chair-seated position and, in random sequence, in the last 16 min of a 60-min supine rest. RESULTS: Overall, systolic BP (SBP) and diastolic BP (DBP) decreased by 11.6 and 4.3 mm Hg, respectively, during the chair-seated rest; only a 1.8-mm Hg decrease in SBP was observed in the control supine study. The chair-seated fall in BP was associated with a decrease in systemic vascular resistances, in the absence of significant changes in cardiac index. From the logarithmic curve of SBP and DBP decrements, a half-time of 5.8 and 5.5 min respectively, was calculated. Decrements in SBP, but not DBP, were inversely related to the corresponding baseline values. CONCLUSIONS: In untreated essential hypertensive patients a significant decrease in SBP and DBP associated with a systemic vasodilation was observed during a 16-min rest in the chair-seated position. Because approximately 75% of the spontaneous fall in BP occurred within 10 min, it appears that this time at rest before clinic BP evaluation could improve the precision and accuracy of the measurement.

What is the accuracy of clinic blood pressure measurement?

BACKGROUND: In clinical practice, blood pressure (BP) is frequently measured at the end of the visit in patients sitting on one side of the bed and not on a chair according to guidelines. METHODS: In 540 consecutive subjects with essential hypertension (EH) attending a hospital outpatient clinic, BP was measured in the following sequence: 1) patient seated on chair for at least 5 min, 2) patient supine, 3) patient seated on bed, and 4) patient standing for a few minutes. RESULTS: We found that mean (+/-SEM) BP was 143.5/87.2 +/- 0.9/0.5, 153.4/89.7 +/- 1.0/0.5, 148.9/90.9 +/- 1.0/0.5, and 144.8/91.7 +/- 1.0/0.6 mm Hg, respectively (P < .05 v position 1 for all). In 14% of patients, either systolic BP (SBP) or diastolic BP (DBP) was above the conventional upper limits of normality in the seated-on-bed but not in the recommended seated-on-chair position ("false" high clinic BP), whereas SBP and DBP were "false" normal (below limit for bed-seated and above limit for chair-seated position) in only 6% and 2% of patients, respectively. Overall, SBP and DBP increments from the chair- to the bed-seated position were inversely related to the baseline chair-seated values; systolic increments were directly related to age, in particular in the subgroup of untreated EH (n = 70), and to body mass index. A gender-related difference was apparent, as female subjects had more pronounced increments in SBP (+7.4 +/- 0.8 v +3.5 +/- 0.7 mm Hg) and DBP (+4.4 +/- 0.5 v 2.9 +/- 0.4 mm Hg) than did male subjects (P < .05 for both). CONCLUSIONS: Clinic SBP and DBP are overestimated in the bed-seated position at the end of the visit compared with the recommended chair-seated position in treated and untreated patients with EH, in particular in elderly obese women with mild hypertension.