The measurement of arterial properties in hypertension

A promoter polymorphism of lamin A/C gene is an independent genetic predisposition to arterial stiffness in a Japanese general population (the Tanno and Sobetsu study)

AIM

We examined the hypothesis that there is a positive, independent association between polymorphisms of lamin A/C gene (LMNA) and arterial stiffness in Japanese.

METHODS

The subjects were 261 men (mean age, 64.4+/-0.7 years) selected from inhabitants of the towns of Tanno and Sobetsu in a rural area of Japan who underwent medical check-ups. We conducted clinical examinations, including measurement of bilateral brachial-ankle pulse wave velocity (baPWV) as a marker of arterial stiffness, and genetic analysis. Subjects with atrial fibrillation, subjects with ankle-brachial index <0.9, and subjects taking any medication were excluded. We selected two single nucleotide polymorphisms (SNPs) as markers of LMNA, 1908C/T in exon 10 and -1030C/T in the promoter region, which we have recently identified. All genotypes were clearly determined by the TaqMan PCR method.

RESULTS

Genotype frequencies of the two polymorphisms satisfied the Hardy-Weinberg equilibrium. The baPWV of -1030C/T polymorphism was significantly greater in subjects with CC genotype than in subjects with CT+TT genotype (1,652+/-22.1 cm/s vs. 1,552+/-43.0 cm/s, p=0.039); however, no significant difference was found for 1908C/T polymorphism. The baPWV was found to be significantly associated with age, body height, systolic blood pressure, and smoking habit; therefore, we next performed multiple regression analysis including these parameters, and found an independent, significant association between baPWV and -1030C/T polymorphism.

CONCLUSION

Promoter -1030C/T polymorphism of LMNA is a possible genetic predisposition to arterial stiffness in the Japanese population.

Novel measures of cardiovascular health and its association with prevalence and progression of age-related macular degeneration: the CHARM Study

Background

To determine if novel measures of cardiovascular health are associated with prevalence or progression of age-related macular degeneration (AMD).

Methods

Measures of the cardiovascular system: included intima media thickness (IMT), pulse wave velocity (PWV), systemic arterial compliance (SAC), carotid augmentation index (AI). For the prevalence study, hospital-based AMD cases and population-based age- and gender-matched controls with no signs of AMD in either eye were enrolled. For the progression component, participants with early AMD were recruited from two previous studies; cases were defined as progression in one or both eyes and controls were defined as no progression in either eye.

Results

160 cases and 160 controls were included in the prevalence component. The upper two quartiles of SAC, implying good cardiovascular health, were significantly associated with increased risk of AMD (OR = 2.54, 95% CL = 1.29, 4.99). High PWV was associated with increased prevalent AMD. Progression was observed in 82 (32.3%) of the 254 subjects recruited for the progression component. Higher AI (worse cardiovascular function) was protective for AMD progression (OR = 0.30, 95%CL = 0.13, 0.69). Higher aortic PWV was associated with increased risk of AMD progression; the highest risk was seen with the second lowest velocity (OR = 6.22, 95% CL = 2.35, 16.46).

Conclusion

The results were unexpected in that better cardiovascular health was associated with increased risk of prevalent AMD and progression. Inconsistent findings between the prevalence and progression components could be due to truly different disease etiologies or to spurious findings, as can occur with inherent biases in case control studies of prevalence. Further investigation of these non-invasive methods of characterizing the cardiovascular system should be undertaken as they may help to further elucidate the role of the cardiovascular system in the etiology of prevalent AMD and progression.

Outcomes of treating hypertension in the elderly: a short commentary on current issues

Because treating hypertension in the elderly so effectively reduces major cardiovascular events, it is vital to diagnose this very common condition early. Much of the hypertension that occurs with aging results from stiffening of the major capacitance arteries, typically marked by high systolic and low diastolic blood pressures. Pulse pressure, derived by subtracting diastolic from systolic values, is a useful index of stiffness, but new noninvasive techniques for measurement of arterial compliance have shown that blood pressures cannot reliably predict the state of the arteries in older people. The Systolic Hypertension in the Elderly Program (SHEP) and the Systolic Hypertension in Europe (Syst-Eur) trial demonstrated that treating hypertension in the elderly with diuretics or calcium channel blockers reduces strokes and cardiac events; these results are also clearly evident in high-risk groups like diabetics. Further analysis of Syst-Eur has suggested that a calcium channel blocker reduces new-onset dementia, while follow-up data from SHEP indicate that a diuretic provides survival and stroke benefits in obese or overweight elderly hypertensives, but not in the lean. In general, comparisons of antihypertensive agents, including diuretics, beta blockers, angiotensin-converting enzyme inhibitors, and calcium channel blockers have found similar clinical end point effects. But recently, the Losartan Intervention For End Point Reduction in Hypertension (LIFE) study, performed in patients (average age, 67) with left ventricular hypertrophy and predominant systolic hypertension, showed that the angiotensin receptor blocker losartan was significantly more effective than the beta blocker atenolol in reducing such key outcomes as strokes and new-onset diabetes. Even so, careful but effective control of blood pressure in elderly patients, including those over age 80, still remains a critical factor in preventing major cardiovascular events.

Effect of antihypertensive agents on arterial stiffness as evaluated by pulse wave velocity: clinical implications

Structural and functional properties of the arterial wall have been reported to be altered in hypertension, even at early stages of the disease. Morbidity and mortality associated with hypertension are primarily related to arterial damage that may affect one or several organs. Considering the potential implications of arterial assessment in the prevention of cardiovascular disease, evaluation of the arterial effects of antihypertensive agents is recommended by numerous authorities. Among the noninvasive and simple methods to evaluate large arteries, pulse wave velocity (PWV) measurement is widely used as an index of regional arterial stiffness. This method is related to the arterial geometry and wall function, simple and reproducible, and thus, can easily be applied in clinical trials. Several studies performed in various populations showed significant powerful interactions between PWV and cardiovascular risk factors. In addition, aortic PWV was shown to be a forceful marker and predictor of cardiovascular risk in normotensive individuals and patients with hypertension. Furthermore, aortic PWV was shown to be an independent predictor of all-cause mortality in patients with essential hypertension. In comparison with placebo, clinical studies have shown that in short and long term trials, antihypertensive agents improved arterial stiffness (as evidenced by a reduction in PWV) independently of blood pressure reduction. The decrease of PWV was more pronounced with long term treatment than with short term treatment. Whether antihypertensive agents differ in their arterial effects independently of blood pressure changes remains unclear. Pharmacological studies, generally performed in small numbers of patients, indicate that the effects of long term treatment with ACE inhibitors, calcium channel antagonists and some beta-blockers on arterial stiffness are generally similar. The effectiveness of an antihypertensive agent in reducing arterial stiffness may also be influenced by the genetic background of the patient. Recently, the Complior Study has shown the feasibility to assess arterial stiffness in clinical trials involving large populations using an automatic device for measuring PWV. Long term treatment with an ACE inhibitor, perindopril, was associated with a decrease in blood pressure and aortic PWV in patients with essential hypertension. In high risk patients with end-stage renal failure, ACE inhibitors effectively decreased arterial stiffness and had a favorable effect on survival which was independent of changes in blood pressure. The correlation between reversion of arterial stiffness and decrease in cardiovascular morbidity and mortality needs to be confirmed in populations of patients with lower cardiovascular risk.