Pulmonary Arterial Hypertension
Adjusting Therapy in Pulmonary Arterial Hypertension – The Role of Novel Echocardiographic Techniques
John G Coghlan1 and Denis Pellerin2 1. Royal Free Campus; 2. The Heart Hospital, University College London
Abstract
In theory, echocardiography allows an accurate measurement of pulmonary artery pressure, approximate right atrial pressure, cardiac output, right ventricular diastolic function and non-volumetric assessment of systolic function, as well as some insight into the structural alterations of right ventricular architecture. Unfortunately, the vast array of possible measures complicates distillation of the few parameters that provide reproducible prognostically important information. The modest reductions in afterload achieved with current therapies (
Keywords Contrast echocardiography, speckled tracking, strain rate imaging, vector velocity imaging, right ventricle
Disclosure: The authors have no conflicts of interest to declare. Received: 30 April 2010 Accepted: 9 June 2010 Citation: European Cardiology, 2010;6(2):38–42 Correspondence: John G Coghlan, Department of Cardiology, Royal Free Hospital, Pond Street, London, NW3 2QG, UK. E:
Gerry.Coghlan@royalfree.nhs.uk
Goals in Pulmonary Arterial Hypertension Treatment
Pulmonary arterial hypertension (PAH) arises from pathological thickening, obstruction and constriction of the pulmonary arterioles.1 This leads to progressive elevation of pulmonary pressures initially on exertion, then at rest.2
Symptoms present late, often only when the
pressures can rise little further and the cardiac output (CO) falls due to right ventricular (RV) overload.3
As the condition progresses
towards the end stage, the right heart dilates and exhibits reduced function, resulting in clinical evidence of heart failure. With rare exceptions, current therapies yield modest reductions in pulmonary pressures, but by reducing pulmonary vascular resistance lead to significant increases in CO. The function and size of the right heart improves slightly and the clinical benefit is modest. As the gains in terms of RV function and pulmonary pressures are modest, techniques that focus on these aspects of cardiac function are relatively insensitive to the changes that are achieved with treatment.
The objectives of treatment have been outlined in the recent European Society of Cardiology and European Respiratory Society (ESC/ERS) guidelines. The domains identified are clinical (functional class 1 or 2, no blackouts, with no evidence of heart failure), exercise
(six-minute maximum walking distance [6MWD] >500m, O2 consumption on exercise >15ml/kg/minute) and objective (normal N-terminal portion of proBNP [NTproBNP], tricuspid annular plane systolic elevation [TAPSE] >20mm, absence of pericardial effusion, right atrial pressure [RAP] 2.5l/minute). Failure to achieve these objectives is an indication to increase
38
Ultimately, we require therapies that will reverse the haemodynamic process and normalise pulmonary artery pressure (PAP). Therefore, the ability to accurately measure PAP remains a pivotal goal for non-invasive tests. In addition, improving right ventricular function is an important secondary goal, thus reproducible and accurate assessment of RV systolic and diastolic function will eventually help to guide therapy.
Recent Echocardiographic Imaging Techniques Contrast Echocardiography
Contrast echocardiography may be performed with agitated saline solution to improve the signal quality of Doppler flow recordings.4,5 Contrast echocardiography may also improve endocardial border detection and assessment of cavity sizes and function.6
Myocardial Doppler Velocity and Myocardial Isovolumic Acceleration
Myocardial motion is characterised by relatively low-velocity and high- amplitude signals. 2D images have good spatial resolution, whereas spectral Doppler and M-mode have the best temporal resolution.7,8 Myocardial velocities quantify global and regional left ventricular (LV) function independently of endocardial border delineation. Tissue
© TOUCH BRIEFINGS 2010
treatment.3
Therefore, at a simplistic level we already have echocardiographic criteria for adjusting PAH therapy. In reality, most patients do not achieve these goals, and there have been no randomised trials to demonstrate that goal-directed therapy improves survival or quality of life.
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