Hypertension in Special Populations: Athletes

Rosa Maria Bruno; Giulia Cartoni; Stefano Taddei


Future Cardiol. 2011;7(4):571-584. 

In This Article

Clinical Evaluation

Diagnosis of Arterial Hypertension

As recommended by the current guidelines, for any patient, in the diagnosis of arterial hypertension several blood pressure measurements should be taken on separate occasions over a period of weeks or months.[4] In particular, if blood pressure is only slightly elevated, the period of observation could be longer.[4] Caution must be taken in diagnosing hypertension in competitive athletes, since their sports activity may be greatly restricted as a consequence of a wrong diagnosis. Some specific aspects require attention in dealing with this special population. First, in children and adolescents blood pressure reference values in the age-adjusted tables based upon gender and height percentile should be considered, as stated in the recently published guidelines: hypertension is diagnosed only if blood pressure values exceed the 95th percentile by more than 5 mmHg.[39] With regard to blood pressure measurement equipment, an appropriately sized cuff should be used: this is important for children and adolescents, who may require a smaller cuff, as well as for athletes in whom arm musculature is strongly represented, where an inappropriately small cuff could lead to overestimation of blood pressure values and thus to false positives.

Another important issue concerning blood pressure measurement should not be disregarded. Although office blood pressure remains the reference blood pressure measurement method, exclusion of white coat hypertension is mandatory. White-coat hypertension, better named isolated clinic hypertension, is characterized by the presence of persistently increased blood pressure values in the clinical setting, accompanied by normal home or 24-h values.[4] This condition has a prevalence of about 15% in the general population.[40,41] Since evidence of its adverse prognostic relevance is less consistent in outcome studies, as compared with both office and ambulatory blood pressure elevation;[40,41] thus, its treatment is not currently recommended.[4] In a study conducted on 410 football players at the annual preventive check (mean age 16 years), 41 athletes out of 410 (10%) were detected as having elevated systolic or diastolic blood pressure in the first office measurement. However, 18 athletes out of 410 (4.4%) had blood pressure above the accepted normal levels after two or more office blood pressure measurements, and only two athletes had 24-h ambulatory blood pressure measurement values >140 and/or 90 mmHg.[42] Although the threshold considered in the above-mentioned study was not the currently accepted level (125–130/80 mmHg),[4] and evidence on 24-h-blood pressure monitoring in athletes is lacking, it appears reasonable to recommend a 24-h ambulatory blood pressure measurement in athletes with persistently elevated office blood pressure values, especially if they do not present any evidence of target organ damage. Unfortunately, in athletes the issue of isolated clinic hypertension and masked hypertension, defined as the presence of raised home and/or 24-h blood pressure values in the presence of normal office values, is largely unaddressed. Further studies are required to clarify the prevalence of these conditions in athletes and the clinical approach to them.

Finally, hypertension specialists are frequently asked to evaluate athletes with exaggerated blood pressure response to exercise testing, in the presence of either normal or increased resting blood pressure values. This issue is particularly complex, first of all because there is no widely accepted definition of exertional hypertension:[43] some studies consider as cut off the 90°–95° percentile, others a fixed number; moreover, while some authors consider peak values, others consider blood pressure in the recovery period or at a chosen heart rate.[43] A simpler way to define exaggerated blood pressure response to exercise testing could be peak systolic blood pressure >210 mmHg for men and >190 mmHg for women.[44] Considering the athletes' population, a small study suggested that endurance-trained athletes reached higher maximum systolic blood pressure values at the peak of exercise, as well as of heavier workloads; however, these athletes demonstrated higher systolic blood pressure even at lower and comparable workload.[45] By contrast, another study demonstrated that women with low cardiorespiratory fitness were more likely to present a higher blood pressure response during submaximal exercise.[46] In the general population, there was also conflicting evidence as regards the possible negative prognostic role of blood pressure response to exercise testing independently of resting blood pressure values.[47,48] Consequently, such rises should not be a reason to restrict physical activity.[49] However, subjects with an excessive rise in blood pressure during exercise are more prone to develop hypertension.[44,50] Thus, although there is no consensus about the clinical approach in this particular case, it appears reasonable to recommend to regularly check blood pressure, either at home or in a clinical setting, in order to promptly intervene if hypertension develops.

Screening for Secondary Causes

The prevalence of secondary hypertension in athletes is expected to be the same as in the general population, and the physician should follow current guidelines in order to identify patients in whom a secondary cause of hypertension is suspected, taking into account medical history, physical examination, and routine tests.[4] However, certain special situations must also be considered. Wheelchair athletes with spinal cord injuries above T6 level may have severe episodic hypertension in the case of self-induced autonomic dysreflexia (commonly known as boosting), which is a massive sympathetic discharge induced by nociceptive stimuli. Experimental evidence indicates that self-induced boosting can improve performance time by 10% in elite wheelchair marathon racers during simulated racing. Since it can be dangerous to health, the International Paralympic Committee has banned athletes from voluntarily inducing boosting during competition.[51]

Drug-induced hypertension should be carefully ruled out. This phenomenon concerns over-the-counter medications, including NSAIDs, and oral contraceptive pills (commonly taken by female athletes), but also herbal and dietary supplements used to increase energy or control weight. These preparations often contain 'natural' substances such as guarana, ma huang, and ephedra, which are stimulants. Interestingly, most of the commonly used performance-enhancing drugs, such as androgen-anabolic steroids, growth hormone, erythropoietin, or stimulants such as amphetamines, caffeine, ephedrine and pseudoephedrine and cocaine have negative cardiovascular effects, including hypertension.[52] The physician should investigate with caution the possible use of doping substances not only in elite competitive athletes, but also in nonprofessional sports athletes.

Stratification of Cardiovascular Risk

Once arterial hypertension is diagnosed and secondary causes of hypertension are ruled out, the next step is a global cardiovascular risk assessment, as recommended by current guidelines.[4] This is a crucial issue, since prognosis in each patient depends on identification and treatment of all risk factors, not only hypertension. Furthermore, risk stratification allows identification of patients at higher risk, in whom antihypertensive treatment should be started promptly. Presence of other clinical conditions should also guide the choice of the drug and establish different blood pressure goals Table 2.

The physician should follow the normal routine to test for the presence of classical cardiovascular risk factors, such as family history of premature cardiovascular disease, lipid and glucose status alterations, abdominal obesity and smoking; and established cardiovascular or renal disease, target organ damage, metabolic syndrome or diabetes, as these conditions automatically put the hypertensive patient at high or very high added risk Table 2. Mandatory diagnostic procedures include: repeated blood pressure measurements, medical history, physical examination, routine laboratory investigations (fasting plasma glucose; total, HDL and LDL cholesterol; triglycerides, potassium, uric acid, creatinine, complete blood count and urinalysis) and ECG.[4] Additional specific aspects in athletes must be considered. With regard to cardiovascular risk factors, certain doping substances, such as growth hormone and androgenic–anabolic steroids, per se cause metabolic disturbances both in lipid and glucose homeostasis, or may favor cardiovascular events either through their direct prothrombotic effect (erythropoietin) or by causing vasospasm (cocaine) or arrhythmias (cocaine and other stimulants).[52]

In the assessment of target organ damage, the physician should proceed as recommended in current hypertension guidelines,[4] with some differences. Urinalysis, including microalbuminuria, is among routine laboratory investigations to be performed in hypertensive patients. In athletes false positive results are likely, since exercise-induced proteinuria, a benign and reversible phenomenon, may occur if vigorous physical activity is performed in the 24 h before the test.[53] Echocardiography and exercise testing (with ECG and blood pressure monitoring), which are not always included in evaluation of the hypertensive patient, are warranted as routine tests in the hypertensive athlete, according to guidelines endorsed by the European Society of Cardiology.[54]

Systematic training in endurance or isometric sports may trigger physiologic adaptations and reversible structural cardiac remodeling, including increased left ventricular wall thickness, enlarged ventricular and atrial volumes, thus leading to increased calculated cardiac mass, in the presence of normal systolic and diastolic function. In general, the most frequent alteration found during echocardiography is increased left ventricular mass, associated with normal or increased fractional mid-wall shortening, and high left ventricular volume.[55–56] Increased left ventricular wall thickness is common in body builders,[57] whereas it is usually normal or minimally increased in other sport practitioners.[55,56] Indeed, only about 2% of highly trained subjects have left ventricular wall thickness >12 mm.[58] Taken together, these aspects identify the so-called 'athlete's heart'.[58] Athlete's heart is also associated with a variety of abnormal 12-lead ECG patterns, present in about 40% of elite athletes. Such patterns frequently mimic those of cardiac disease (increased R- or S-wave voltages, Q waves and repolarization abnormalities).[59] Characteristics associated with athlete's heart include male gender, black ethnicity and ultra-endurance sport disciplines with a high isotonic and isometric component.[58] In young competitive athletes the crucial issue is the differential diagnosis between athlete's heart and with hypertrophic cardiomyopathy, but also with dilated cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy.[58] The differentiation between athlete's heart and hypertrophic cardiomyopathy is crucial, since the latter is the commonest cause of nontraumatic exercise related sudden cardiac death in young athletes.[8] Systematic evaluation consisting of a detailed physical and family history, the demographics of the athlete, 12-lead ECG and echocardiography are mandatory first-line investigations. Subsequent investigation with cardiopulmonary exercise testing, cardiac MRI assessment following detraining and screening for causal genetic mutations may be necessary in equivocal cases.[58] On the other hand, in hypertensive athletes the physician should distinguish between athlete's heart and left ventricular hypertrophy. The echocardiographic pattern described above can be differentiated by the classical hypertensive cardiac disease, particularly from the concentric left ventricular hypertrophy, in which the increased mass is determined by increased wall thickness, with normal left ventricular volume.[55,56] The differentiation with an eccentric hypertrophy, which is a not infrequent pattern in hypertensive patients, can be more challenging. The main criterion accepted in differentiating athlete's heart from hypertensive left ventricular hypertrophy is the normality of both systolic and diastolic function, whereas in hypertension-induced left ventricular hypertrophy a certain degree of impaired diastolic filling is often present.[60] Thus the echocardiographist should evaluate comprehensively systolic and diastolic function, including mid-wall fractional shortening, mitral valve annular peak systolic velocity, mitral inflow doppler pattern and tissue doppler study of diastolic filling.[58–59,61] Normality of backscattering analysis[62] and of circumferential strain and torsion[63] in athlete's heart were also reported. Left ventricular hypertrophy beyond the 'athlete's heart' should limit participation until the blood pressure is normalized and the possibility of hypertrophic cardiomyopathy has been fully assessed.[54–55,64]

Current guidelines recommend the usefulness of exercise testing in all hypertensive athletes.[54] Performing exercise testing in all hypertensive patients could help identifying not only silent ischemic disease, but also to diagnose exertional arrhythmias, which require further examinations to exclude the presence of silent arrhytmogenic structural cardiac diseases.[65]

This point of view is questioned by some authors, since such athletes are a population with a low probability of coronary heart disease and a significant prevalence of left ventricular hypertrophy: in these conditions a significant proportion of positive tests on electrocardiography are expected to be falsely positive.[11] However, there is a general consensus that in the case of asymptomatic patients who are going to engage intense (>60% of maximum) exercise training, and patients with high/very high cardiovascular risk who are going to engage low-to-moderate leisure time physical activity, a medically supervised peak or symptom-limited exercise test is warranted, as well as in the presence of cardiac symptoms. exercise testing should be performed.[11,25,66] Cardiopulmonary exercise testing may help distinguish between hypertrophic cardiomyopathy from physiologic left ventricular hypertrophy in athletes[67] and may be more accurate than ECG exercise testing when prescribing exercise training in patients with established cardiac disease.[68] However, in general, there is no specific indication to cardiopulmonary exercise testing in hypertensive patients without cardiac disease. Stress myocardial scintigraphy or echocardiography, and coronary angiography, may be indicated in cases of doubt.[11,66]

Establishing Sports Eligibility

According to the consensus document endorsed by the European Society of Cardiology and the 36th Bethesda Conference, sports eligibility in hypertensive patients depends on three factors: severity of hypertension, global cardiovascular risk profile of the patient and the type of sport performed.[54,57] In the currently accepted classification, sports are considered according to the type and intensity of exercise, and also with regard to the danger of bodily injury from collision, as well as the possible harmful consequences of syncope Table 3. Exercise can be divided into two broad types: dynamic (isotonic) and static (isometric).[57] Dynamic exercise involves changes in muscle length and joint movement with rhythmic contractions that develop a relatively small intramuscular force; static exercise involves development of a relatively large intramuscular force with little or no change in muscle length or joint movement. This is a rough simplification, since most physical activities usually involve both static and dynamic components, but is very useful in order to determine whether it is reasonably safe to recommend that an athlete with a specific cardiovascular abnormality be eligible for a particular competitive sport. Sports are further classified according to the level of intensity in low, medium and high intensity Table 3. The recommendations for competitive sports participation in athletes with arterial hypertension but without established cardiovascular disease are summarized in Table 4.[54] To achieve sports eligibility, blood pressure should be lowered to the recommended threshold, which is 140/90 mmHg in all hypertensive patients irrespective of their degree of risk, by means of pharmacological or nonpharmacological treatment.[5] Mild hypertensive athletes with no other cardiovascular risk factors should not be restricted in their sports activity, once blood pressure is controlled Table 4. On the other hand, athletes with grade 2 or 3 hypertension, even in the absence of any other risk factor and after normalization of blood pressure values, are not eligible for highly demanding sports. When present, risk factors other than hypertension must be controlled, as their presence could be a contraindication for some sports categories, as highlighted in Table 4. Hypertensive patients with associated clinical conditions, in particular ischemic heart disease, should be evaluated according to the appropriate guidelines.[54,69]