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管心血管疾病仍是美國的主要死因,但其發生率在過去20年中持續下降。這一趨勢主要歸功於心血管危險因子的檢測和管理水平的提高。弗雷明漢心臟研究的開創性工作自1940年代末開始追蹤受試者,有助於揭示諸如高齡、高血壓、吸煙、血清膽固醇升高、糖尿病、左心室肥厚和肥胖等因素帶來的風險。由於這項持續的研究,臨床醫生對如何改變心血管風險有了更深入的了解,從而有望繼續降低死亡率。 (《美國心臟雜誌》1988; 116:266。)心血管疾病是工業化國家的主要死因。在美國,最常見的心血管疾病是冠狀動脈疾病,每年造成55萬人死亡和125萬例心臟事件。然而,在過去的20年裡,美國心血管疾病死亡率下降了33%,每年可能挽救了多達25萬人的生命。同時,中風死亡率也下降了。 拒絕50%。 ² 這些趨勢最可能的解釋是,由於檢測和治療的改進以及生活方式的改變,心血管疾病風險因素有所減少。 ³
弗雷明漢心臟研究收集了過去36年的數據,為心血管疾病的風險因素提供了寶貴的見解。這項研究始於1940年代末,共招募了5,209名男性和女性(均為麻薩諸塞州弗雷明漢居民),年齡介於30歲至62歲之間。在詳細了解病史後,這些受試者接受了全面的身體檢查、血液檢查、心電圖評估和胸部X光檢查。他們每兩年回來進行追蹤評估,目前正在進行第二十個週期的檢查。 ⁴
迄今為止,超過一半的最初受試者已經死亡,主要死因是心血管疾病。這些事件為我們提供了大量關於該疾病病因及其誘發因素的資訊。
例如,分析表明,男性心血管疾病的發生率幾乎隨年齡增長呈線性增加(圖1)。 ⁵ 另一方面,女性在停經前患有此類疾病極為罕見;女性的發生率比男性滯後15至20年。 ⁵
除了年齡之外,其他已知的風險因素還包括高血壓、吸菸、血清膽固醇水平升高、糖尿病、左心室肥厚和肥胖。值得注意的是,所有這些因素都是可以改變的。
高血壓的作用
對弗雷明漢研究數據的回顧顯示,高血壓在年輕人中相當少見,但隨著年齡增長,男性和女性的盛行率均上升。到大約 65 歲時,近 40% 的受試者被發現有高血壓。目前,研究族群中大部分是老年人(80 歲以上),且盛行率持續上升。 ⁵
對這些患者的觀察有助於消除許多關於高血壓與冠狀動脈疾病風險之間關聯的誤解。 ⁶ 首先,研究發現血壓與心血管疾病之間的關係是連續的,從遠低於 通常認為的血壓水平就開始發揮作用。高血壓一般來說,血壓越低,風險越低。此外,與普遍認知相反,老年人對血壓升高的耐受性並不比年輕人好。事實上,在任何血壓水平下,老年人罹患冠心病的相對風險都更高(圖2)。
另一個常見的誤解是,高血壓與心血管風險之間的流行病學關係僅限於舒張壓而非收縮壓水平。與此觀點相反,弗雷明漢研究的調查人員和其他研究人員都觀察到,收縮壓和舒張壓與預後的相關性同樣顯著。這原理對於老年族群尤其重要,因為老年族群中收縮性高血壓的盛行率高於舒張性高血壓。
弗雷明漢研究的數據也揭示了降血壓治療如何改變這些關係。研究期間,接受降血壓藥物治療的高血壓患者比例顯著增加,從約30%增加到70%。同時,血壓控制達標的高血壓患者比例也從約25%增加到70%。由於採取了更積極的治療措施,高血壓的發生率下降。同時,中風的發生率也出現下降;這種下降在女性中尤為顯著,但在男性中則不明顯。
與中風發病率的良好趨勢相反,儘管高血壓管理水平有所提高,但過去三十年來冠狀動脈疾病的發生率幾乎沒有變化。這種缺乏改善的原因一直令觀察者困惑不已,尤其是在高血壓與心血管疾病風險之間的關聯如此顯著的情況下。
對弗雷明漢研究數據的回顧提供了一些線索,或許有助於闡明這個難題。對接受治療和未接受治療的高血壓男性進行比較發現,前者實際上猝死的風險更高(圖3)。 多重危險因子乾預試驗(MRFIT)的亞組分析也得出了類似的結論。 這些觀察結果引發了人們對降血壓藥物治療潛在不良反應的擔憂,尤其是加重心律不整的風險。
為了更深入研究這些關係,我們分析了弗雷明漢研究數據,以確定687例接受利尿劑治療且無心血管疾病證據的高血壓患者中室性心律不整的發生率;並將結果與1031例未接受治療的高血壓 患者進行比較。我們發現,在接受利尿劑治療的患者群中,某些類型室性心律不整的年齡校正風險有增加的趨勢。相較之下,100例接受β受體阻斷劑治療的高血壓患者的心律不整發生率降低(圖4)。 ⁹ 新型降血壓療法在多大程度上(如果有的話)能夠降低冠心病的發生率,還需要進一步研究。
吸煙者與非吸煙者
弗雷明漢研究的數據也被用來分析吸菸對冠心病(包括急性心肌梗塞)風險的影響。結果顯示,與非吸菸者相比,吸菸者罹患心血管疾病的風險通常增加兩倍(圖 5)。有趣的是,無論吸的是過濾嘴香菸或非過濾嘴香菸,這種關聯都成立。弗雷明漢研究¹¹近期也證實了吸菸與中風風險之間有密切關聯。
膽固醇數據
血清膽固醇升高或許是心血管疾病中最常被誤解的危險因子。 1950 年收集的來自弗雷明漢健康男性(年齡 30 至 49 歲)的數據顯示,隨著基線血清膽固醇水平從 <204 mg/dl 升高至 ≥295 mg/dl,患有冠狀動脈疾病的風險呈階梯式增加。 ¹² 因此,膽固醇似乎會持續增加心血管疾病的風險,即使膽固醇水平低至 200 mg/dl 也開始增加。 MRFIT 研究人員也觀察到了非常相似的現象,他們報告稱,冠狀動脈疾病的風險呈階梯式增加,從膽固醇水平約為 180 mg/dl 開始。 ¹³
最近發表的一份關於弗雷明漢膽固醇數據的報告回顧了1950年基線膽固醇水平測量的受試者在30年隨訪期間的生存率。分析顯示,31至39歲的年輕健康男性中,基線血清膽固醇水準低於180 mg/dl者死亡率較低。膽固醇水平在180至220 mg/dl之間的人群死亡率略高,而膽固醇水平在220至260 mg/dl之間的人群死亡率則更高。基線膽固醇水平超過260 mg/dl的人群死亡率最高,令人擔憂。 ¹⁴
這些發現對確定最佳膽固醇水平具有重要意義。數據顯示,膽固醇水平在 220 至 260 mg/dl 之間與較高的心血管風險有關。一些臨床觀點認為,即使是 180 至 220 mg/dl 之間的膽固醇水平也值得關注。儘管關於具體閾值的討論仍在繼續,但研究普遍表明,維持較低的總膽固醇水平與降低冠心病及其相關併發症的風險之間存在相關性。
然而,總血清膽固醇水平僅能提供心血管風險綜合評估的一部分。 近年來,我們越來越意識到,低水平的高密度脂蛋白(HDL)膽固醇同樣會增加風險。弗雷明漢研究收集的男性和女性的資料顯示,隨著基線HDL膽固醇水平的升高,心血管疾病的風險顯著降低(圖6)。當HDL水準≥65 mg/dl時,風險極低。 <sup>15</sup>
因此,在評估整體風險時,顯然必須同時考慮總膽固醇和高密度脂蛋白膽固醇(HDL-C)水平。在HDL-C篩檢普及之前,我們可能認為總膽固醇水平為190 mg/dl的患者罹患心血管疾病的風險並不高。然而,如今,如果我們發現這類患者的HDL-C水平為35 mg/dl,我們就會意識到其風險實際上非常高。反之,如果患者總膽固醇水平為260 mg/dl,我們過去可能會建議其徹底改變生活方式和飲食習慣,甚至可能需要藥物幹預。但憑藉現有的檢測方法,如果我們發現這類患者的HDL-C水平高於60 mg/dl,我們就會認為其心血管疾病的風險並未增加。
肥胖
肥胖已被認為是富裕人群心血管疾病的重要可控因素。 <sup>16</sup>弗雷明漢研究發現肥胖與心血管疾病的發生與發展之間存在關聯。 <sup>17</sup>然而,脂肪組織在評估中的作用一直存在爭議。 <sup>16</sup>關於脂肪組織如何促進特定危險因子、其對風險的獨立貢獻以及肥胖模式的影響等問題仍未得到解答。 <sup>16-17</sup>
對弗雷明漢隊列進行30年的追蹤顯示,體重指數(衡量肥胖的指標)和肩胛下皮褶厚度處於最高三分之一的人群(圖7)全因死亡率、中風、心臟衰竭和冠心病風險增加。心血管事件發生率往往隨著全身肥胖和腹部肥胖程度的增加而增加。
相對體重增加和腹型肥胖程度均與心血管危險因子負擔加重有關,包括血清總膽固醇、血壓、血糖、尿酸和總膽固醇/高密度脂蛋白膽固醇比值。體重變化往往伴隨著這些危險因子的相應變化,體重每波動15磅,這些危險因子的變化趨勢呈線性。肥胖相關的部分(但非全部)心血管風險增加可歸因於這些危險因子的惡化。
由於體重對主要心血管危險因子的影響,控制體重是預防 心血管疾病的重要一環。然而,要達到顯著且持久的減重,還需要採取其他措施。
糖尿病
隨著年齡增長,人體葡萄糖耐受性會逐漸下降。然而,這並非無關緊要的衰老現象。在任何年齡段,糖尿病都會獨立地導致所有主要的動脈粥狀硬化性疾病,包括冠狀動脈心臟病、腦梗塞、週邊動脈疾病和心臟衰竭。由於冠心病的發生率較高,因此它是最常見的心血管後遺症。
糖尿病是少數幾種會消除女性相對於男性優勢的致動脈粥狀硬化代謝因素之一。糖尿病對女性所有心血管後遺症的影響都比男性更大。
糖尿病患者的心血管危險因子負擔往往比非糖尿病患者更重。心血管疾病風險增加的大部分可歸因於此,但似乎也存在一些獨特的效應,這可能與血栓形成增強有關。
糖尿病對心血管疾病的影響差異很大,取決於相關的心血管風險因素。由於風險很大程度上受合併風險因子水準的影響,因此糖尿病控制的概念應擴展至包括整個心血管風險因子的正常化。
風險因素的相互作用
弗雷明漢研究也檢視了8年期間發生冠狀動脈疾病的機率與已確定的各種風險因素之間的關係。透過建構一個針對健康、不吸菸的40歲男性(心電圖和血壓正常,膽固醇水平正常,且無左心室肥厚或糖尿病證據)的風險評估模型,數據顯示其冠狀動脈疾病風險極低(圖8)。如果此風險評估模型改變,例如血清膽固醇升高,風險會增加約四倍。如果再增加其他危險因子(例如糖尿病、吸菸、心電圖異常或左心室肥厚),風險會進一步增加。例如,對於一位40歲的糖尿病患者,如果同時吸菸、患有高血壓且血清膽固醇升高,則風險會增加100倍。 ¹⁵
從另一個角度審視這些問題,可以推薦一些臨界值來制定治療策略,以期獲得最佳的風險狀況。 基於弗雷明漢研究數據,我們可以得出結論:除非總膽固醇低於150 mg/dl,否則總膽固醇與高密度脂蛋白膽固醇的比值應≤4.5。血壓應維持在<140/90 mmHg的水平。應建議吸菸者戒菸,吸食雪茄和煙鬥的吸菸者也應如此。糖尿病患者必須嚴格控制血糖。此外,應將體重指數維持在<22 kg/m²。
結論
在過去三十年間,弗雷明漢心臟研究已確定了多種心血管疾病風險因素,包括高齡、高血壓、吸菸、高血脂、糖尿病、左心室肥厚和肥胖。過去二十年間,美國心血管疾病死亡率顯著下降。可以說,弗雷明漢研究的開創性工作促成了這一重大轉變,它使臨床醫生能夠評估患者的風險因素,並採取措施最大限度地減少不良心血管事件的發生。Cardiovascular risks: New insights from Framingham pdf英文全文
July 1988 Julius American Heart Journal Volume 116 Number 1, Part 2
Daniel Levy, MD>b and William B. Kannel, MDb Frumingham and Boston, Muss., and Bethesda, Md.
Although cardiovascular disease remains the leading cause of death in the United States, its incidence has decreased steadily during the past 20 years. This trend is largely attributable to improved detection and management of cardiovascular risk factors. The pioneering work of the Framingham Heart Study, which has followed subjects since the late 19408, has helped shed light on the risks conferred by factors such as advancing age, hypertension, smoking, elevated serum cholesterol, diabetes, left ventricular hypertrophy, and obesity. As a result of this ongoing investigation, clinicians have gained a better understanding of the ways in which cardiovascular risks can be modified so that mortality rates will hopefully continue to decline. (AM HEART J 1988; 116:266.) Cardiovascular disease is the leading cause of death in industralized nations. In the United States, the most common form of cardiovascular disease is coronary artery disease, which accounts for 550,000 deaths and 1,250,OOO cardiac events each year.’ During the past 20 years, however, the incidence of mortality from cardiovascular disease has decreased by 33% in the United States, perhaps saving as many as 250,000 lives annually. At the same time, the incidence of death from stroke has declined 50%.² The most likely explanation for these trends is a reduction in cardiovascular risk factors as a result of improved detection and treatment, as well as life-style modifications.³
Valuable insights into risk factors for cardiovascular disease have emanated from the Framingham Heart Study, which has collected data for the past 36 years. Beginning in the late 1940s, this investigation enrolled 5209 men and women (all residents of Framingham, Mass.), who ranged in age from 30 to 62 years. After thorough histories were obtained, these subjects underwent extensive physical examinations, blood tests, ECG assessments, and chest x-ray films. They have returned for follow-up assessments every 2 years and are currently undergoing the twentieth cycle of examinations.⁴
To date more than half the original subjects have died, primarily of cardiovascular disease. These events have provided a wealth of information on the cause of the disease as well as its predisposing factors.
For example, analyses have shown that the incidence of cardiovascular disease in men increases in an almost linear fashion with advancing age (Fig. 1).⁵ On the other hand, in women such disease is extremely uncommon before menopause; the incidence in women lags 15 to 20 years behind that in men.⁵
Apart from age, factors identified as conferring increased risk include hypertension, smoking, elevated serum cholesterol levels, diabetes, left ventricular hypertrophy, and obesity. It is important to note that all these factors are amenable to modification.
ROLE OF HYPERTENSION
A review of the Framingham data reveals that hypertension is fairly uncommon in young persons but increases in prevalence with advancing age in both men and women. By approximately 65 years of age, nearly 40% of the subjects were found to be hypertensive. At present much of the study population is elderly (over the age of 80 years), and the prevalence has continued to increase.⁵
Observations in these patients have helped dispel many myths regarding the association between hypertension and the risk of coronary artery disease.⁶ First, the relationship between blood pressure and cardiovascular disease has been found to be continuous, beginning at levels well below those typically regarded as hypertensive. The general rule of thumb is, the lower the blood pressure, the lower the risk. In addition, contrary to widespread belief, blood pressure elevations are not tolerated better by the elderly than by younger persons. In fact, at any level of blood pressure the elderly exhibit a greater relative risk of coronary disease (Fig. 2).
Another common misconception is that the epidemiologic relationship between hypertension and cardiovascular risk extends only to levels of diastolic rather than systolic blood pressure. Contradicting this notion, both the Framingham investigators and other workers have observed that systolic and diastolic pressures correlate equally well with outcome. This principle is of particular importance with regard to the elderly, in whom systolic hypertension is more prevalent than diastolic hypertension.
The Framingham data have also provided insights into how these relationships may be altered via the use of antihypertensive therapies. During the study the proportion of hypertensive subjects receiving such agents has increased dramatically—from approximately 30% to 70%. At the same time, the proportion of hypertensive subjects attaining blood pressure control has increased from approximately 25% to 70%. As a consequence of more aggressive management, the incidence of hypertension has declined. A concomitant decrease in the incidence of stroke has been observed; this reduction has been significant among women but not among men.
In contrast to the favorable trend with regard to stroke, the incidence of coronary artery disease has changed little during the past 3 decades despite improved hypertension management. The reason for this lack of effect has baffled observers, particularly since the relationship between hypertension and the risk of cardiovascular disease is so compelling.
A review of the Framingham data yields some clues that may help shed light on this dilemma. A comparison of treated and untreated hypertensive men shows that the former group actually sustained a higher risk of sudden cardiac death (Fig. 3).7 Subgroup analyses from the Multiple Risk Factor Intervention Trial (MRFIT) have yielded similar findings.8 These observations have given rise to concern regarding the potentially adverse effects of antihypertensive drug therapy, particularly aggravation of arrhythmias.
To examine these relationships more closely, we analyzed the Framingham data to determine the incidence of ventricular arrhythmias in 687 diuretic-treated hypertensive patients who were free of any evidence of cardiovascular disease; the findings were compared with those in 1031 untreated hypertensive subjects. We identified a trend toward an increased age-adjusted risk of some forms of ventricular arrhythmias in the group receiving diuretics. In contrast, the rate of arrhythmias was decreased among 100 hypertensive patients treated with β-blockers (Fig. 4).⁹ The extent, if any, to which newer antihypertensive therapies can reduce the incidence of coronary disease will require additional investigation.
SMOKERS VS NONSMOKERS
The Framingham data have also been analyzed to determine the effect of smoking on the risk of both coronary heart disease in general and acute myocardial infarction in particular. The results show that smokers generally have a twofold increased risk of cardiovascular disease compared with nonsmokers (Fig. 5). Interestingly, this relationship has held true regardless of whether filtered or nonfiltered cigarettes have been smoked. A strong relationship between smoking and stroke risk has also been recently demonstrated in the Framingham Study.¹¹
CHOLESTEROL DATA
Elevated serum cholesterol is perhaps the most widely misunderstood risk factor for cardiovascular disease. Data gathered in 1950 from healthy Framingham men 30 to 49 years of age show that the risk of developing subsequent coronary artery disease increases stepwise as baseline serum cholesterol levels rise across the population from <204 to ≥295 mg/dl.¹² Therefore it appears that cholesterol increases the risk of cardiovascular disease along a continuum, beginning at levels as low as 200 mg/dl. A remarkably similar observation was made by the MRFIT investigators, who reported a stepwise increase in the risk of coronary artery disease, starting at cholesterol levels of approximately 180 mg/dl.¹³
A recently published report on the Framingham cholesterol data reviewed survival rates during 30 years of follow-up of subjects whose baseline levels were measured in 1950. The analysis showed that among young, healthy men, ages 31 to 39 years, those with baseline serum cholesterol levels <180 mg/dl had a slow rate of mortality. Those with levels ranging from 180 to 220 mg/dl died at a slightly faster rate, and the rate among those with levels of 220 to 260 mg/dl was faster still. The most alarmingly rapid mortality rate was seen in the group exhibiting baseline cholesterol levels in excess of 260 mg/dl.¹⁴
These findings have important implications for determining optimal cholesterol levels. Data suggests that levels ranging from 220 to 260 mg/dl are associated with higher cardiovascular risks. Some clinical perspectives suggest that even levels between 180 and 220 mg/dl may warrant attention. While discussions regarding specific thresholds continue, research generally indicates a correlation between maintaining lower total cholesterol levels and a reduced risk of coronary disease and related health complications.
However, total serum cholesterol levels provide only one part of a comprehensive cardiovascular risk assessment. only part of the picture. In recent years we have become more aware of the fact that low levels of high-density lipoprotein (HDL) cholesterol likewise increase risk. Information gathered in Framingham men and women has revealed that the risk of developing cardiovascular disease decreased dramatically as baseline levels of HDL cholesterol increased (Fig. 6). At HDL levels ≥65 mg/dl, the risk was extremely low.15
Thus when assessing overall risk, it is clear that both total and HDL cholesterol levels must be taken into consideration. Before the availability of HDL screening, we may have considered that a patient with a total cholesterol level of 190 mg/dl was not at increased risk for cardiovascular disease. Today, however, if we found that such a patient had an HDL level of 35 mg/dl, we would recognize that the risk is actually extraordinarily high. Conversely, faced with a patient whose total cholesterol is 260 mg/dl, we may have previously recommended sweeping life-style changes and dietary modifications and possibly pharmacologic intervention. With the methodology now available to us, if we were to find that such a person had an HDL cholesterol level >60 mg/dl, we would recognize that the risk of cardiovascular disease was not increased.
OBESITY
Obesity has been implicated as an important modifiable contributor to cardiovascular disease in affluent populations.16 Investigations in the Fra-mingham Study have found a connection between obesity and the subsequent development of cardiovascular disease.¹⁷ Nevertheless, the role of adiposity in the evaluation has been controversial.¹⁶ Questions remain about its promotion of specific risk factors, its independent contribution to risk, and the influence of the pattern of obesity.¹⁶⁻¹⁹
A 30-year follow-up of the Framingham cohort has shown an increased risk of all-cause mortality, stroke, cardiac failure, and coronary disease in persons who were in the upper tertile of body mass index (a measure of obesity) and subscapular skinfold thickness (Fig. 7). Cardiovascular event rates tended to increase with the degree of general and abdominal obesity.
Both increased relative weight and degree of abdominal obesity are associated with an increased burden of cardiovascular risk factors, including serum total cholesterol, blood pressure, glucose, uric acid, and total/HDL cholesterol ratio. Changes in weight tend to be mirrored by corresponding changes in these risk factors, with linear trends observed for a 15-pound fluctuation in weight. Some but not all of the increased cardiovascular risk associated with obesity is attributable to this worsening of risk factors.
Because of the influence of weight on the major cardiovascular risk factors, weight control is an important feature of a preventive program against cardiovascular disease. However, other measures are sorely needed for achieving substantial, sustained weight loss.
DIABETES
Progressive impairment of glucose tolerance occurs as persons age. However, this cannot be viewed as an innocuous aging phenomenon. At all ages, diabetes contributes independently to all the major atherosclerotic disease outcomes, including coronary disease, brain infarction, peripheral arterial disease, and cardiac failure. Because of its greater incidence, coronary heart disease is the most common cardiovascular sequela.
Diabetes is one of the few atherogenic metabolic factors that eliminates the female advantage over men. Diabetes has a greater impact on all cardiovascular sequelae in women than in men.
Diabetic patients tend to have a larger burden of cardiovascular risk factors than nondiabetic persons. Much of the excess risk of cardiovascular disease can be ascribed to this, but there also appears to be some unique effect that may be attributable to enhanced thrombogenesis.
The impact of diabetes on cardiovascular disease is quite variable, depending on the associated cardiovascular risk profile. Since the risk is greatly influenced by the level of coexistent risk factors, the concept of diabetes control should be broadened to include normalization of the entire cardiovascular risk profile.
INTERACTIONS OF RISK FACTORS
The Framingham Study also examined the probability of developing coronary artery disease over an 8-year period in relation to the various risk factors identified. By developing a profile for a healthy, nonsmoking 40-year-old man with a normal ECG and blood pressure, normal cholesterol levels, and no evidence of left ventricular hypertrophy or diabetes, the data shows that the risk of coronary disease is very low (Fig. 8). If this profile is altered such that serum cholesterol is elevated, the risk is increased approximately fourfold. If other risk factors are then added (such as diabetes, smoking, ECG abnormalities, or left ventricular hypertrophy), the risk increases further. For instance, in a 40-year-old diabetic person who smokes, is hypertensive, and has elevated serum cholesterol, the risk would be increased 100-fold.¹⁵
Examining these concerns from the opposite perspective, certain cutoff values can be recommended to devise therapeutic strategies. directed toward producing an optimal risk profile. Based on the Framingham data, we can conclude that the ratio of total to HDL cholesterol should be ≤4.5 unless total cholesterol is <150 mg/dl. Blood pressure should be maintained at a level of <140/90 mm Hg. Cigarette smokers should be advised to quit, as should cigar and pipe smokers who inhale. Patients with diabetes must be kept under strict glycemic control. In addition, a body mass index <22 (kg/m²) should be maintained.
CONCLUSIONS
During the past 3 decades, the Framingham Heart Study has identified numerous risk factors for cardiovascular disease, including advancing age, hypertension, smoking, hyperlipidemia, diabetes, left ventricular hypertrophy, and obesity. During the past 2 decades, the incidence of mortality from cardiovascular disease has declined dramatically in the United States. It is safe to say that the pioneering work of the Framingham Study has contributed to this momentous change by allowing clinicians to assess the presence of risk factors in their patients and institute measures to minimize adverse cardiovascular outcomes.









