Right Atrial Function in Hypertension

Home , Atrium (heart)

NAY Chung and GYH Lip Haemostasis Thrombosis and Vascular Biology Unit, University Department of Medicine, City Hospital, Birmingham B18 7QH, UK

Keywords: right atrium; hypertension

The heart is pathophysiologically related to the ation with a right coronary artery occlusion may pathogenesis of hypertension, but unfortunately, result in a decrease in right ventricular compliance, also suffers its consequences. Indeed, changes in left as well as a marked reduction in right ventricular ventricular size, structure and function, as well as filling and stroke volume, leading to impaired left (more recently) the left atrium in patients with ventricular filling, hypotension or even shock.6 hypertension are well described, and are regarded Indeed, hypotension in relation to right ventricular as manifestations of ‘hypertensive heart disease’.1 infarction is managed by increasing right heart fill- In particular, the presence of left ventricular ing pressures by the administration of fluids. Right hypertrophy (LVH), which is the main adaptive ventricular systolic function has also been found to response of the ventricular myocardium in response have prognostic significance in patients with con- to the increased pressure load of hypertension, is gestive cardiac failure7 and pulmonary thromboem- associated with ultrastructural changes in the myo- bolic disease.8 In patients with hypertension, the cardium, leading particularly to left ventricular dia- presence of right ventricular wall thickening and stolic dysfunction,1 activation of neurohormonal septal hypertrophy, with diastolic dysfunction par- systems (such as catecholamines, the renin-angio- alleling that of the left ventricle, have been tensin-aldosterone system, etc),2 coagulation abnor- reported.9 Raised pulmonary artery pressures and malities3 and possibly, insulin resistance.4 Indeed, pulmonary arteriolar resistance are also found in abnormalities of systolic and diastolic function may such patients,10 but whether this is the cause for the be a feature of hypertensive heart disease,1 which raised right ventricular pressures is still unclear. are accompanied by changes in the left atrium. For In this issue of the Journal of Human Hyperten- example, Dernellis et al5 reported that hypertensive sion, the study by Dernellis11 reports on abnormali- patients have larger left atrial volumes, atrial reser- ties of right atrial function (decreased right atrial voir function and atrial ejection force, to compen- E/A ratio and increased A wave integral and right sate for the effect of LVH and diastolic dysfunction. atrial active contribution) in hypertensives com- This latter is also evident by the reduction in E wave pared to controls, as well as the (beneficial) effects and reversed E/A ratio of the mitral valve inflow pat- of antihypertensive therapy with amlodipine or ram- tern on Doppler echocardiography.1 ipril. Other findings which normalised after treat- As with many examples in clinical practice, the ment were a reduction in passive flow into the right presence of the multitude of abnormalities in the left ventricle, as well as reduction in total transtricuspid side of the heart has led to relative inattention to the right ventricular filling, which was accompanied by right side. Indeed, the right side of the heart has an increase in right ventricular isovolumetric relax- often been neglected as its contribution to cardio- ation time (RV IVRT) and right atrial active contri- vascular function was (erroneously) thought to be bution (RAAC) to right ventricular filling. negligible. By contrast, the right atrium is an Importantly, there appeared to be an independent important contributor to right ventricular stroke vol- relationship to left ventricular mass and right ven- ume, and indirectly, left ventricular filling. As a tricular relaxation. Thus, left ventricular mass clear example of the importance of the right side of appears to affect right atrial function as well as left the heart, a right ventricular infarction in associ- atrial function, perhaps via its influence on left and right ventricular diastolic function. In addition, we should not forget that the right Correspondence: Dr GYH Lip, Haemostasis Thrombosis and Vas- cular Biology Unit, University Department of Medicine, City Hos- atrium not only acts as a reservoir but also contains pital, Birmingham B18 7QH, UK. E-mail: G.Y.H.LIPȰbham.ac.uk the supraventricular conducting system. Whilst ven- Received and accepted 17 October 2000 tricular arrhythmias are known to be common with Right atrial function in hypertension NAY Chung and GYH Lip 440 LVH, the incidence of atrial fibrillation and other pulmonary tree, other ACE inhibitors and calcium supraventricular arrhythmias is much higher in channel blockers have been studied in pulmonary hypertensive patients.12 The co-existence of atrial hypertension and hypoxia.18,19 The effect of capto- fibrillation and hypertension are both additive to the pril and nifedipine on pulmonary vascular tone in stroke and thromboembolic risk, and such patients sheep has also been studied, with reductions in pul- represent a ‘high risk’ group.13,14 The development monary arterial pressure and pulmonary vascular of atrial fibrillation in patients with diastolic dys- resistance.20 function secondary to hypertensive LVH may also The role of the right atrium is often overlooked in result in a dramatic reduction in stroke volume, due hypertension, and it appears that right atrial func- to loss of atrial transport, leading to heart failure.1 tion is significantly abnormal in hypertension, and Right atrial thrombus is generally considered an is normalised with antihypertensive therapy, with uncommon phenomenon, but perhaps we may not ramipril being superior to amlodipine.11 However, be looking hard enough. The right atrial appendage the clinical implications of abnormal right atrial is larger than its left counterpart and has a wide function in hypertensives still remain uncertain. opening into the main atrial chamber. In compari- Whether the observed abnormalities contribute to son, the left atrial appendage is longer, narrower and heart failure amongst hypertensives, the develop- more hooked than the right and is constricted at its ment of supraventricular arrhythmias, or throm- atrial junction. Thus, perhaps one would expect to boembolism (albeit asymptomatic, if thrombi are not find a higher incidence of thrombus in the left atrial easily visualised in the right atrial appendage on appendage. Indeed, atrial thrombi in hypertension echocardiography), and whether the improvement per se is very rare, although their presence in atrial in right atrial function by treating hypertension fibrillation, particularly in the left atrial appendage translates to prognostic benefit, requires more data, as compared to the right,15 is well documented and including randomised trial evidence. this could feasibly result in thromboembolism. Moreover, there is increasing evidence that patients Acknowledgements with hypertension demonstrate abnormalities of haemostasis, platelets and endothelial function in We acknowledge the support of the City Hospital keeping with a prothrombotic or hypercoagulable NHS Trust Research & Development Programme. state.3 Whilst LVH and raised left atrial pressures could partly explain the increase in pulmonary References artery pressures, the study by Olivari et al10 suggests that these raised pulmonary pressures are unlikely 1 Lip GYH et al. Hypertensive heart disease: a complex to be secondary to impairment of left ventricular syndrome or a hypertensive ‘cardiomyopathy’? Eur function per se. Certainly, neurohormonal influ- Heart J 2000; 21: 1653–1665. ences on the pulmonary vascular tree may be one 2 Unger T. Neurohormonal modulation in cardiovascu- factor. lar disease. Am Heart J 2000; 139: S2–S8. 3 Lip GYH, Li-Saw-Hee FL. Does hypertension confer a The reduction of blood pressure and left ventricu- hypercoagulable state? J Hypertens 1998; 16: 917–123. lar mass by ACE inhibitors is well documented, and 4 Prichard B et al. Hypertension and insulin resistance. these effects may alter right atrial function, as in the J Cardiovasc Pharmacol 1992; 20 (Suppl 11): S77–S84. study by Dernellis.11 For example, ramipril has been 5 Dernellis JM et al. Effects of antihypertensive therapy shown to be as effective as beta-blockers, calcium on left atrial function. J Hum Hypertens 1996; 10: antagonists and diuretic therapy in reducing blood 789–794. pressure, but is significantly better at reducing left 6 Berger PB, Ryan TJ. Inferior myocardial infarction. ventricular mass.16,17 In such comparison, ramipril High-risk subgroups. Circulation 1990; 81: 401–411. was significantly better than amlodipine at reducing 7 DiSalvo TG et al. Preserved right ventricular ejection left ventricular mass and systolic function, as well fraction predicts exercise capacity and survival in advanced heart failure. J Am Coll Cardiol 1995; 25: as RV IVRT and the normalisation of right atrial 1143–1153. function. The greater efficacy of ACE inhibitors in 8 Wolfe MW. Prognostic significance of right ventricular reducing left ventricular mass may in part be related hypokinesis and perfusion lung scan defects in pul- to the effect of the renin-angiotensin system on the monary embolism. Am Heart J 1994; 127: 1371–1375. sympathetic system as well the reduction in after- 9 Myslinski W et al. Right ventricular function in sys- load and the antagonism of local angiotensin II.1 temic hypertension. J Hum Hypertens 1998; 12: 149– Another possibility to explain the effect(s) on right 155. atrial function by treating hypertension10 may be 10 Olivari MT et al. Pulmonary haemodynamics and right that the changes seen on RV IVRT could simply be ventricular function in hypertension. Circulation a manifestation of the effects of the drug on the pul- 1978; 57: 1185–1190. 11 Dornellis JM. Right atrial function in hypertensive monary vasculature. The renin-angiotensin system patients: effects of antihypertensive therapy. J Hum certainly has a role in the pulmonary circulation Hypertens 2001; 15: 463–470. causing vasoconstriction, which may be further 12 Kannal WB et al. Epidemiologic features of chronic exacerbated by hypoxia. Whilst there is no evidence atrial fibrillation. NEJM 1982; 306: 1018–1022. looking at ramipril and amlodipine directly on the 13 Du X et al. Stroke risk from multiple risk factors com-

Journal of Human Hypertension Right atrial function in hypertension NAY Chung and GYH Lip 441 bined with hypertension: a primary care based case- 17 Aepfelbacher FC et al. Disparate effects of ACE inhibi- control study in a defined population of north-west tors and calcium antagonists on left ventricular struc- England. Ann Epidemiol 2000; 10: 380–388. ture and function in essential hypertension. J Hum 14 Atrial Fibrillation Investigators. Risk factors for stroke Hypertens 1997; 11: 321–325. and efficacy of antithrombotic therapy in atrial fibril- 18 Bertoli L et al. Effects of captopril on haemodynamics lation. Analysis of pooled data from five randomised and blood gases in chronic obstructive lung disease controlled trials. Arch Intern Med 1994; 154: 1449– with pulmonary hypertension. Respiration 1986; 49: 1457. 251–256. 15 DeDivitiis M et al. Right atrial appendage thrombosis 19 Sajkov D et al. A comparison of two long-acting vaso- in atrial fibrillation: its frequency and its clinical pre- selective calcium antagonists in pulmonary hyperten- dictors. Am J Cardiol 1999; 84: 1023–1028. sion secondary to COPD. Chest 1997; 111: 1622–1630. 16 Roman MJ et al. Differential effects of angiotensin con- 20 Yoshimura K et al. Effects of angiotensin converting verting enzyme inhibition and diuretic therapy on enzyme inhibitor and calcium channel blocker on nor- reductions in ambulatory blood pressure, left ventricu- moxic and hypoxic pulmonary vascular tone in unan- lar mass, and vascular hypertrophy. Am J Hypertens aesthetised sheep. Jpn Circ J 1987; 51: 1138–1146. 1998; 11: 387–396.

Journal of Human Hypertension