DISCUSSIONS

Role of Isolated Systolic Hypertension.
Population-based long-term follow up are urgently needed to demonstrate the association of risk factors with hypertension in Asia; however, prevention programs should be started based on cross-sectional surveys and cases studies without waiting for cohort studies⁵. Therefore, we realized that in the present study, the prevalence of ISH at elderly hypertensive patients was 36 % but most practitioners usually missed since they only diagnosed as simple hypertension. Nevertheless, over the past four decades, numerous studies have examined the influence of drug treatment of hypertension on the risk of cardiovascular events. The average reduction in DBP of 5-6 mmHg in these trials conferred a reduction of about 38% in stroke incidence, a 16% reduction in CHD events, a 21% reduction in all vascular events and a 12% reduction in all-cause mortality²². However, nowadays, the role of ISH is especially important. The recent observational epidemiological studies and randomized controlled trials have demonstrated that SBP is an independent and strong predictor of risk of cardiovascular and renal disease²⁴. The Multiple Risk Factor Intervention Trial (MRFIT) was a randomized, multicenter, primary prevention trial to assess the combined influence of BP, serum cholesterol level, and cigarette smoking on death from CAD. Data on risk factors were available for 316,099 white men aged 35 to 57 with no prior history of MI or diabetes after an average follow-up of 12 years has shown that SBP is a better indicator of increased risk of coronary artery disease than DBP²³. A review 10 randomized trials with a total of 18.542 participants, antihypertensive treatment was associated 21% reduction in total (fatal and non-fatal) CHD events and 37% reduction in fatal stroke. An average reduction of 14-15 mmHg in SBP over 4 years confers 21% reduction in CHD, 37% reduction in stroke, 25% reduction in total cardiovascular mortality and 13% reduction in all-cause mortality^24-26. J A Staessen et al reviewed the results of the three outcome trials in older patients with ISH (SHEP, SYST-EUR, SYST-CHINA) were pooled. Overall, active treatment reduced all-cause mortality by 17% and cardiovascular mortality by 25% compared with placebo²⁵. In the Framingham study, SBP was used in the scoring system in order to assess the absolute risk 10 years for hard coronary artery disease^13-14. From the INDANA project steering committee, Stuart et al presented the calculation of risk of CVD with five years have also used SBP to calculate score in the 11 risk factors to quantify an adult's risk of death from CVD including stroke and CHD²⁸. Therefore, we need to have an early attention and intervention about the ISH in the elderly for active treatment in daily clinical practice.

Coexisting Risk Factors with Hypertension
The mean summation of major risk factors was different significantly between Vietnamese males and females with P < 0.001 (Table 3). The proportions of patients with one, two, three and more additional risk factors were similar with INSIGHT (Figure 8). Does this issue explain the development of the 'second wave' epidemic of CVD that is flowing thought developing countries? Compared with the baselines of the addional risk factors of INSIGHT and ALLHAT, there was not much different^4,29(Figure 7). In generally, our summation of risk factors was similar with the ones in the developed countries. The proportion of the family history of CVD was lower than in the INSIGHT (5.2 vs. 20) and the proportion of hypercholesterolemia was also lower than in both INSIGHT and ALLHAT. Possibly, these differences may explain why the incidence of stroke is higher than heart disease in Vietnam as well as in the South East ASIA¹². This problem requires to study further future scrutiny. However, if the total cholesterol level were over 2 g/l, the proportion of hypercholesterolemia would be 49 %. The proportion of HDL-C < 35 mg/dl was 51%. According to the ATP III, HDL-C < 40 mg/dl is as the major and independent risk factor. In the Heart Protection Study, treatment with statins even in the subjects with LDL-C level < 100mg/dl have also decreased significant their cardiovascular mortality^30,39. Therefore, we must pay on more attention on these major risk factors in the hypertensive patients. For type II diabetes is now considered a cardiovascular disease more than a metabolic disease³¹, the proportion of diabetes coexisting with hypertension was similar with the proportion in developed countries (Figure 7). Nowadays, ATP III raised persons with diabetes but without CHD to the risk level of CHD risk equivalent¹³. Both JNC VI and 1999 WHO/ISH placed the hypertensive patients who have diabetes into the very high-risk group with the goal of treatment of less than 130/85 mmHg^1,16. In Europe and Canada, the current recommendations for the diabetic patients without nephropathy are that BP be reduced to = 130/80 mmHg and that DBP of < 80 mmHg is deemed safe^17,9. While obesity and physical inactivity are defined as major risk factors by AHA, we noted the proportion of these risk factors were very low in our patients in comparison with the Western countries³². The other risk factors of uncertain significance such as homocyserine, lipoprotein a, fibrinogen, C-reactive protein and plasmin renin were not observed in this study.

Application of Guidelines 1999 WHO/ISH on Clinical Practice.
We noted the ratio of hypertension at the grade 3 was the lowest but as evaluated for stratifying risk, the ratio of the very-high-risk group was the highest. These are the preeminent points of these guidelines; differences in risk of CVD are determined not only by the level of BP, but also by the presence or levels of other risk factors. The stratification of patients by absolute level of cardiovascular risk is very important to quantify prognosis and appropriate therapy; however, most clinicians have not evaluated adequately this problem. Until now, we have had too many guidelines for assessment of cardiovascular risk factors^13-21. In every guideline, there are major and independent risk factors identified, but they vary so much from one guideline to another ^1,13-20,33. There are also too many methods to calculate a patient's absolute cardiovascular risk (Framingham risk equations, CVD life expectancy model, Dundee coronary risk disk, PROCAM risk function, British regional heart study risk function etc…)³³. Therefore, it is necessary for the World Heart Organization/World Heart Federation to have a common, universal guideline to assess the cardiovascular risk factors in order to have better application of the guidelines into the real world. It is difficult for the local physicians to confront the plethora of tremendous amounts of available information, which confuse the medical practitioners at the front line. Guideline should be simple, clear, evidence-based, effective, and easily applicable into routine daily practice. We need measures to improve adherence, which focus on the physician and medical office, the heath deliver system and the patient. While the JNC VI and even JNCVII, which will be released in the next few months, continue to recommend a diuretic or beta-blocker as first-line therapy unless there are compelling or specific indications for another drug³⁸, the proportion of prescribing these classes of drug in Vietnam has been very limited. Is the pharmaceutical industry responsible for this problem? Thus, we need to pay more attention on different aspect of prescribing medications for hypertension such as effectiveness, lower side effect profile, simple regimen, affordability to the patients.


CONCLUSION

Cardiovascular risk assessment is an important addition to the doctor's diagnostic and prognostic black bag. However, this study showed that there was little evidence that the clinical practice has improved. Guidelines are widely acknowledged but largely ignored. Therefore, we need to have a univesary guideline and the new strategies of better applying theses guidelines for management of hypertension as well as of other risk factors in clinical practice with optimal treatment to improve the quality of life of patient: live longer, live healthier, live happier.

Acknowledgments
The author wishes to acknowledge Pr Thach Nguyen from St Mary University Merryville in Indiana, Pr Sunil Das from Michigan University, and Pr Norman M Kaplan from Texas USA for their insightful, invaluable comments and encourages. He also thanks to the students Thach Cong Luan, Do Huu Nguyen for their contributions to this study.