Enzo Porteri

Prognostic Significance of Small-Artery Structure in Hypertension

Background—The presence of structural alterations in the microcirculation may be considered an important mechanism of organ damage; however, it is not currently known whether structural alterations of small arteries may predict fatal and nonfatal cardiovascular events. Methods and Results—One hundred twenty-eight patients were included in the present study. There were 59 patients with essential hypertension, 17 with pheochromocytoma, 20 with primary aldosteronism, 12 with renovascular hypertension, and 20 normotensive patients with non-insulin-dependent diabetes mellitus. All subjects were submitted to a biopsy of subcutaneous fat. Small resistance arteries were dissected and mounted on an isometric myograph, and the tunica media-to-internal lumen ratio (M/L) was measured. The subjects were reevaluated after an average follow-up time of 5.4 years. Thirty-seven subjects had a documented fatal or nonfatal cardiovascular event (5.32 events/100 patients per year). In the subcutaneous small arteries of subjects with cardiovascular events, a smaller internal diameter and a clearly greater M/L was observed. Our subjects were subdivided according to the presence of an M/L greater or smaller than the mean and median values observed in the whole population (0.098) or mean value +2 SD of our normal subjects (0.11). Life-table analyses showed a significant difference in event-free survival between the subgroups. Cox’s proportional hazard model, considering all known cardiovascular risk factors, indicated that only pulse pressure (P =0.009) and M/L (P <0.0001) were significantly associated with the occurrence of cardiovascular events. Conclusions—Our results strongly indicate a relevant prognostic role of structural alterations in small resistance arteries of a high-risk population.

Structural Alterations in Subcutaneous Small Arteries of Normotensive and Hypertensive Patients With Non–Insulin-Dependent Diabetes Mellitus

Background — It is not presently known whether non–insulin-dependent diabetes mellitus (NIDDM) is associated with the presence of structural alterations in small arteries or whether the combination of hypertension and NIDDM may have an additive effect on endothelial dysfunction. Therefore, we investigated subcutaneous small arteries in 12 normotensive subjects (NT group), 18 patients with essential hypertension (EH group), 13 patients with NIDDM, and 11 patients with NIDDM and EH (NIDDM+EH group). Methods and Results — Subcutaneous small arteries were evaluated by a micromyographic technique. The internal diameter, the media-to-lumen ratio, remodeling and growth indices, and the collagen-to-elastin ratio were calculated. Concentration-response curves to acetylcholine, bradykinin, the endothelium-independent vasodilator sodium nitroprusside, and endothelin-1 were performed. The media-to-lumen ratio was higher in the EH, NIDDM, and NIDDM+EH groups compared with the NT group. EH patients showed the presence of eutrophic remodeling, whereas NIDDM and NIDDM+EH patients showed 40% to 46% cell growth. The collagen-to-elastin ratio was significantly increased in the EH and NIDDM+EH groups compared with the NT group. The vasodilatation to acetylcholine and bradykinin was similarly reduced in EH, NIDDM, and NIDDM+EH groups compared with the NT group. The contractile responses to endothelin-1 were similarly reduced in EH, NIDDM, and NIDDM+EH patients. Conclusions — Our data suggest that the effects of NIDDM and EH on small artery morphology are quantitatively similar but qualitatively different and that the presence of hypertension in diabetic patients has little additive effect on small artery morphology and none on endothelial dysfunction.

Vascular Hypertrophy and Remodeling in Secondary Hypertension

It has been proposed that several neurohumoral factors may be involved in the genesis of vascular structural changes (remodeling or hypertrophy) frequently observed in essential hypertension. Therefore, in this study we investigated vascular structural alterations of subcutaneous small resistance arteries in patients with secondary forms of hypertension. The study included 70 participants: 11 with pheochromocytoma, 13 with primary aldosteronism, and 17 with renovascular hypertension; 13 normotensive subjects and 16 patients with essential hypertension served as controls. All subjects were submitted to a biopsy of subcutaneous fat. Small resistance arteries were dissected and mounted on a micromyograph, and media-lumen ratio, media thickness, remodeling index, and growth index were evaluated. Endothelial function was evaluated according to the dose-response curve to acetylcholine. In patients with either primary aldosteronism or renovascular hypertension, a marked increase in media-lumen ratio was observed, whereas in patients with pheochromocytoma, the extent of vascular structural alterations was similar to that observed in patients with essential hypertension. The increase in media-lumen ratio in patients with essential hypertension and with pheochromocytoma was mainly due to vascular remodeling (remodeling index, 93% to 94%), whereas in patients with renovascular hypertension, there was vascular growth (remodeling index, 70%; growth index, 53%). Patients with primary aldosteronism had an intermediate pattern compared with the other two forms of secondary hypertension. An evident impairment of endothelial function was observed in all four hypertensive groups. In conclusion, the renin-angiotensin-aldosterone system seems to be more powerful than the adrenergic system in inducing vascular growth.

Vascular Remodeling and Duration of Hypertension Predict Outcome of Adrenalectomy in Primary Aldosteronism Patients

Remodeling of the resistance arteries is a hallmark of arterial hypertension and predicts cardiovascular events, but it was unknown whether it could also predict the blood pressure response to adrenalectomy of patients with an aldosterone-producing adenoma. Therefore, we investigated the outcome of adrenalectomy as a function of vascular remodeling in the context of the preoperative features of aldosterone-producing adenoma patients. At 2 referral centers for hypertension, we prospectively measured the media:lumen ratio of small arteries from fat tissue of 50 consecutive aldosterone-producing adenoma patients treated with adrenalectomy. The blood pressure response to adrenalectomy was assessed by considering the blood pressure values and the number and dosages of antihypertensive medications. Adrenalectomy significantly (P<0.001) lowered plasma aldosterone (from 27.3±4.9 ng/dL to 8.3±11.2 ng/dL), the aldosterone:renin ratio (from 117±35 to 11±2), and blood pressure (from 163±22/98±2 mm Hg to 133±2/84±1 mm Hg), even despite a reduction (from 141±14 to 100±15; P=0.02) of the score of antihypertensive treatment. It provided cure of hypertension in 30% of the aldosterone-producing adenoma patients, normotension with less antihypertensive therapy in 52%, and improved blood pressure control in the rest. The media:lumen ratio and the known duration of hypertension significantly predicted the blood pressure response to adrenalectomy at univariate and multivariate analyses. Because a long duration of hypertension and/or the presence of vascular remodeling imply lower chances of blood pressure normalization at long-term follow-up postadrenalectomy, these findings emphasize the importance of an early diagnosis of aldosterone-producing adenoma.

Angiotensin-Converting Enzyme I/D Polymorphism and Arterial Wall Thickness in a General Population The Vobarno Study

BACKGROUND It has been reported that the D allele of an insertion/deletion (I/D) polymorphism of the angiotensin I-converting enzyme (ACE) gene is associated with conditions of increased cardiovascular risk, including left ventricular hypertrophy. METHODS AND RESULTS Considering that a genetically determined overactivity of the renin-angiotensin system may influence cardiac as well as vascular growth, we investigated possible relations between ACE I/D genotype and carotid artery wall thickness (B-mode ultrasound) in 199 subjects, 50 to 64 years old, sampled from the general population of Vobarno, a small town in northern Italy. ACE DD genotype was associated with significantly higher common carotid artery intima-media thickness (P = .003). The occurrence of carotid atherosclerotic plaques was similar in the different genotypes. There was no association of the ACE I/D genotype with blood pressure values (either casual of 24-hour ambulatory monitored). CONCLUSIONS ACE DD genotype may be considered a risk factor for the development of common carotid intima-media thickening in our study population.

Angiotensin II Type 1 Receptor A/C1166 Polymorphism Relationships With Blood Pressure and Cardiovascular Structure

The angiotensin II type 1 (AT1) receptor has a key role in mediating the vasoconstrictor and growth-promoting effects of angiotensin II. It has been reported that a polymorphism of the AT1 receptor gene (an A/C transversion at position 1166) may be associated with cardiovascular phenotypes, such as arterial blood pressure and aortic stiffness, that underlie a condition of increased cardiovascular risk. We examined a sample of 212 subjects randomly selected from a general population in northern Italy to investigate the role of AT1 receptor gene polymorphism, in the regulation of blood pressure and cardiovascular growth. We measured blood pressure (both clinic and 24-hour ambulatory recording), left ventricular mass (echocardiography), and carotid artery wall thickness (B-mode ultrasound); we assessed the AT1 receptor genotype by polymerase chain reaction and allele-specific oligonucleotide hybridization. Blood pressure values were lower in CC homozygotes than in heterozygotes and AA homozygotes; the difference was statistically significant for clinic measurements (mean difference for mean blood pressure, -6.6 mm Hg, P = .01; 95% confidence interval, -1.6 to -11.7 mm Hg) but not for ambulatory blood pressure measurements. CC homozygotes also presented a lower incidence of a positive family history of hypertension (P = .027). No statistically significant differences among AT1 receptor A/C1166 genotypes were observed for left ventricular mass or carotid artery wall thickness. We conclude that the present study does not support a major role of the AT1 receptor gene A/C1166 polymorphism as a marker of conditions associated with increased cardiovascular risk.

Effects of long-term antihypertensive treatment with lisinopril on resistance arteries in hypertensive patients with left ventricular hypertrophy.

Objective To evaluate the effects of long-term antihypertensive therapy with the angiotensin converting enzyme inhibitor lisinopril on structural alterations and the endothelial function of small resistance arteries in hypertensive patients with left ventricular hypertrophy. Methods Fourteen patients with left ventricular hypertrophy were treated for 3 years with a lisinoprilbased regimen. Patients underwent an echocardiographic evaluation of left ventricular mass index at baseline, during the first and third years of treatment. At the end of the treatment period, subcutaneous small resistance arteries (obtained by biopsy of the subcutaneous fat from the gluteal region) were dissected and mounted on a micromyograph (Mulvanys technique); the media: lumen ratio was then calculated. Data obtained were compared with those observed for 14 untreated essential hypertensive patients and 14 normotensive subjects, ageand sex-matched. Results In the present study, a significantly lower media: lumen ratio was observed in treated compared with untreated hypertensive patients, although it remained significantly higher than that in normotensive subjects. In treated hypertensive patients a significant reduction in clinic blood pressure was observed. However, their blood pressure remained significantly higher than that in normotensive subjects. Significant correlations between the media: lumen ratio and blood pressure, left ventricular mass index or changes in left ventricular mass index during treatment were observed. The response to acetylcholine administration was reduced in untreated hypertensives compared with that in normotensives. In patients treated with lisinopril, the vasodilatation obtained with the two higher doses of acetylcholine was greater than that in untreated hypertensives, thus suggesting an improvement of endothelial function. Conclusions Long-term therapy based on lisinopril was associated with a smaller media: lumen ratio in the subcutaneous small resistance arteries of hypertensive patients with left ventricular hypertrophy. Our retrospective study confirms previous findings obtained in prospective studies with other angiotensin converting enzyme inhibitors. Endothelial function was probably improved by lisinopril therapy.

Media: lumen ratio in human small resistance arteries is related to forearm minimal vascular resistance.

Background For the evaluation in humans of structural alterations in resistance arteries, most studies have used an indirect index, the measurement of minimal vascular resistance (mean blood pressure divided by maximal postischaemic blood flow) in suitable vascular beds. A sensitive and specific micromyographic technique was recently made available for the study of human small resistance arteries. Whether a correlation really exists between results obtained with the two techniques has not yet been investigated. Objective To evaluate both forearm minimal vascular resistance and media: lumen ratio of omental or subcutaneous small arteries in normotensive subjects and hypertensive patients. Design and methods Thirty-four individuals were included in the study (age range 35–74 years; 24 hypertensive, 10 normotensive). Twenty-five had elective abdominal surgery and nine hypertensive patients had a gluteal biopsy. Omental and subcutaneous small arteries were dissected and mounted on a wire micromyograph (Mulvanys technique), and media: lumen ratio and media thickness were measured. The dose-response curve to noradrenaline was constructed at cumulative concentrations from 3 ± 10–9 to 3 ± 10–5 mol/l. Venous occlusion plethysmography was used to measure blood flow in the forearm, and minimal vascular resistance was calculated from mean blood pressure and postischaemic maximal blood flow (13 min ischaemia plus exercise). Results A statistically significant correlation was found between media: lumen ratio and minimal vascular resistance (r = 0.74, P < 0.001) as well as between media: lumen ratio and systolic (r = 0.44, P < 0.01) and diastolic (r = 0.38, P < 0.05) blood pressures. Similar correlations were observed between media thickness and systolic and diastolic blood pressures. Small arteries from hypertensive patients had a significantly increased reactivity to noradrenaline (by analysis of variance) compared with those from normotensive subjects, in terms of wall tension but not of active media stress. Conclusions The present study demonstrated that the media: lumen ratio of small resistance vessels is significantly related to forearm minimal vascular resistance, suggesting that direct and indirect evaluations of vascular morphology will give similar results.

Cardiac and Vascular Structural Changes: Prevalence and Relation to Ambulatory Blood Pressure in a Middle-aged General Population in Northern Italy: The Vobarno Study

The aims of this study were to determine the prevalence of structural changes in the carotid arteries and heart and the correlation between these changes and the commonly recognized cardiovascular risk factors in the general population. Structural changes in the carotid arteries were defined as the intima-media thickness of the artery measured by B-mode ultrasound. Changes in the heart were defined as left ventricular mass index (LVMI) measured by echocardiography. LVMI values greater than 134 g/m2 in men and greater than 110 g/m2 in women were considered abnormal, indicating the presence of left ventricular hypertrophy. Blood pressure (BP) was measured in the clinic setting with a mercury sphygmomanometer and by 24-hour noninvasive ambulatory monitoring. Hypertension was defined as a sustained systolic BP greater than or equal to 160 mm Hg and/or diastolic BP increase greater than or equal to 95 mm Hg. The study population consisted of 225 subjects (107 women and 118 men) 48 to 64 years old. Prevalence of intima-media thickening (intima-media thickness > 1 mm) was 11% in normotensive subjects and 44% in hypertensive subjects. The presence of plaque (wall thickening with either mineralization or focal protrusion in the lumen at least 50% greater than the surrounding wall, usually > 2 mm) was observed in 35% of normotensive subjects and 44% of hypertensive subjects. The prevalence of left ventricular hypertrophy was 13% in normotensive subjects and 19% in hypertensive subjects. Intima-media thickness in the common and bifurcation segments of carotid arteries correlated well with LVMI (r = .20 and r = .19, respectively; P < .01). Intima-media thickness and LVMI were both positively related to 24-hour monitored BP (P < .01). However, in the multivariate analysis, body mass index (P = .027), sex (P < .001), and 24-hour mean BP (P = .025) were the most significant determinants of LVMI, whereas carotid artery intima-media thickness was found to be associated best with age (P < .001), cigarette smoking (P = .009), serum cholesterol (P = .025), serum glucose (P = .038), and nighttime systolic BP (P = .006). Logistic regression analysis confirmed the association between the presence of plaque and age (P < .001), nighttime systolic BP (P < .05), and cigarette smoking (P < .05); a negative association between plaque and the decrease in mean systolic BP daytime to nighttime was also observed (P < .001). In conclusion, in a general population of unselected middle-aged subjects, carotid wall thickness and LVMI were associated with each other and related to 24-hour BP levels although the major determinants of carotid wall and cardiac structure were different.

Effect of Treatment With Candesartan or Enalapril on Subcutaneous Small Artery Structure in Hypertensive Patients With Noninsulin-Dependent Diabetes Mellitus

Structural alterations of subcutaneous small resistance arteries are associated with a worse clinical prognosis in hypertension and noninsulin-dependent diabetes mellitus (NIDDM). However, no data are presently available about the effects of antihypertensive therapy on vascular structure in hypertensive patients with NIDDM. Therefore, we have investigated the effect of an angiotensin-converting enzyme inhibitor, enalapril, and a highly selective angiotensin receptor blocker, candesartan cilexetil, on indices of subcutaneous small resistance artery structure in 15 patients with mild hypertension and NIDDM. Eight patients were treated with candesartan (8 to 16 mg per day) and 7 with enalapril (10 to 20 mg per day) for 1 year. Each patient underwent a biopsy of the subcutaneous fat from the gluteal region at baseline and after 1 year of treatment. Small arteries were dissected and mounted on a micromyograph and the media-to-internal lumen ratio was evaluated; moreover, endothelium-dependent vasodilation to acetylcholine was assessed. A similar blood pressure-lowering effect and a similar reduction of the media-to-lumen ratio of small arteries was observed with the 2 drugs. Vascular collagen content was reduced and metalloproteinase-9 was increased by candesartan, but not by enalapril. Changes of circulating indices of collagen turnover and circulating matrix metalloproteinase paralleled those of vascular collagen. The 2 drugs equally improved endothelial function. In conclusion, antihypertensive treatment with drugs that inhibit the renin-angiotensin-aldosterone system activity is able to correct, at least in part, alterations in small resistance artery structure in hypertensive patients with NIDDM. Candesartan may be more effective than enalapril in reducing collagen content in the vasculature.