FOR PHYSICIANS

Diagnosis & Referral

The vast majority of patients are suspected to have PH based on the presence of dyspnea (Rich et al.).

Source: Rich et al.

However, there are many other conditions that cause similar symptoms. As such, physical examination and appropriate laboratory testing should be carried out to assess for the presence of PH, as well as other common causes of such symptoms.

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If you suspect a patient has PH the first step should be to perform an echocardiogram, which can indicate the presence of PH and also assess the severity of PH. Echo should measure the maximal tricuspid regurgitant velocity (TRvMax), which is an indicator of PA systolic pressure, and also assess other “secondary” features of PH, including any abnormalities of the right atrium (e.g. enlargement/dilation) and/or the right ventricle (e.g. hypertrophy, dilation, systolic dysfunction). The presence of a TRvmax > 2.8m/s and/or secondary features of PH should signal the possible presence of pulmonary hypertension.

Echo is also important for detecting underlying cardiac issues that can commonly be the cause of PH, e.g. left-sided heart disease such as mitral and/or aortic valve disease or diastolic/systolic left ventricle dysfunction.

Patients with echo features of PH and/or right ventricular abnormalities should ideally be referred to a local PH expert centre for further specific testing and consideration of most effective treatment approaches.

In cases where the symptoms and/or echocardiogram suggest a high likelihood of PAH or CTEPH, referral should be performed immediately and not delayed pending additional investigations.

Basic investigations that should be requested to start to work-up suspected PH include:
1) Chest X-Ray
2) ECG
3) Pulmonary Function Tests
4) Blood Tests (for conditions associated with PH) and an NT-pro-BNP

Patients can also be referred to a local cardiac/pulmonary specialist for:
1) 6 minute walk test
2) Chest CT-Scan
3) V/Q (ventilation/perfusion) Nuclear Lung Scan (to rule out CTEPH)

Finally, when PH is strongly suspected a patient should undergo a right heart catheterization (RHC) at a PH expert centre. RHC is considered the gold standard of PH diagnosis as it is used to directly measure mean Pulmonary Artery Pressure (mPAP); PH is now defined by a mPAP >= 20 mmHg.

An echocardiogram should be performed on all patients suspected of having PH. An echocardiogram is extremely useful in the diagnosis process for all patients with suspected PH as it allows for an estimate to be made about mPAP using a non-invasive approach. An echocardiogram measures sPAP, which can then be used to make an estimate about mPAP. An echocardiogram measures TRvmax, which can then be used to make an estimate about mPAP.

Unfortunately, there isn’t any single echo measurement that can specifically diagnose PH or completely exclude PH. Therefore, it is recommended that a complete echo assessment of a patient with suspected PH include many different echo measures (guidelines: Rudski L et al. in the Journal of American Society of Echocardiography (2015), including: TR velocity and calculation of RVSP, which is typically equal to systolic PAP; abnormalities of the right atrium (e.g. enlargement/dilation); and abnormalities the right ventricle (e.g. hypertrophy, dilation, systolic dysfunction). Right-side chambers should be assessed, especially RA size (normal <18 cm2), RV hypertrophy, RV size, and RV function. It is important to recognize that an echocardiogram by itself cannot diagnose PH, but is critical to assessing the probability of PH and is used to guide further investigation into the possibility of PH.

Limitations of Echocardiogram
There is generally a good correlation between echo assessment of the severity of PH and actual PH severity as measured by RHC (e.g. mPAP). However, it is important to note that echo is only a non-invasive estimate of PH and should not be viewed as concrete proof of PH or lack thereof. Technical limitations in the echo assessment of PH include incomplete Doppler tricuspid regurgitation envelope and poor visualization of inferior vena cava diameter and collapsibility.

ECGs can provide evidence for heart damage, including previous myocardial infarction and arrhythmias. Some features can be suggestive of PH, but can also be seen in other cardiac diseases, so it’s important to use other tests in conjunction with ECGs in order to diagnose PH.
ECGs are frequently normal in patients with PH, so they cannot be used to exclude PH.

Common ECG Features in PH:

P pulmonale
Right axis deviation
Right ventricle hypertrophy
Right ventricle strain
Right bundle branch block

When PH is confirmed, specific blood tests are used to assess possible causes of PH and to assess the severity of PH.

For assessment of possible causes of PH, recommended blood tests include hepatitis and liver function tests, connective tissue disease antibodies, and HIV

To assess the severity of PH, recommended blood tests include N-terminal pro-brain natriuretic peptide (NT-proBNP) or BNP, which are elevated in relation to right ventricular failure.

The most common symptoms of PH among all age groups are shortness of breath with exertion and associated intolerance of physical activity, resulting in an impairment of patients’ ability to be active.

Exercise intolerance resulting from PH can be caused by a multitude of different factors. The increase in pulmonary artery pressure (PAP) in PH is itself associated with exertional dyspnea. Moreover, in more advanced or long-standing PH, the presence of RV failure worsens exercise tolerance because of the RV’s impaired ability to increase cardiac output, which is necessary for exercise. Current research also points to leg skeletal muscle dysfunction and reduced muscle capillarity density and oxygen supply in the blood stream as being factors that affect exercise intolerance in people suffering from PH (Malenfant et al. 2015).

Six-Minute Walk Test (6MWT)

This simple, practical test of exercise capacity is strongly recommended for all PH patients at baseline and during regular follow-up visits over time. The distance walked during the 6MWT is both: (1) a direct measure of a PH patient’s exercise capacity, which is highly correlated with survival, and (2) an important assessment of a PH patient’s response to treatment. Patients with excellent exercise capacity (high 6MWT distance) have a better quality of life and better prognosis for long-term stability and survival. Conversely, falling 6MWT distance is strongly correlated with a high risk for clinical worsening, including worse right-sided (RV) heart failure, need for hospitalization, and high risk of death. Such patients require careful assessment and consideration of more intensive PH therapy.

Chest CT scans are recommended as a diagnostic tool for many PH patients. CT scans can diagnose an underlying lung disease, and CT pulmonary angiogram (CTPA) can be helpful in the assessment of patients with possible CTEPH.

Features of PH on a regular CT scan:

Mosaic pattern of attenuation due to heterogeneous lung perfusion
Vascular abnormalities such as central pulmonary artery dilation
Cardiac changes such as RV hypertrophy and/or dilation

Contrast-enhanced CTPA can provide specific evidence of CTEPH, including specific features of chronic pulmonary thromboembolism (see below).

The enlargement of the main pulmonary artery (PA) on chest CT is one of the most sensitive features of the presence of PH. A PA diameter greater than or equal to 29mm has a positive predictive value of more than 95% and a specificity of 89% for the presence of PH. Increased cross-sectional diameter of the main PA greater than that of the adjacent ascending aorta is also predictive of PH with a positive predictive value of more than 95% and a specificity of more than 90%. (Grosse & Grosse)

Features of CTEPH on a CT scan:

Changes that can be similar to PAH, including mosaic pattern of attenuation, enlarged main/hilar pulmonary arteries, enlarged RV
Peripheral pulmonary opacities suggestive of previous pulmonary emboli with infarction and scarring
Narrowed and/or completely obstructed main, lobar, and/or segmental pulmonary arteries, mural thickening, intraluminal webs and/or bands
Hypertrophied systemic collateral arterial vessels, including bronchial arteries
These changes of CTEPH require knowledge on the part of the radiologist and the appropriate scan features (1.25mm or thinner slice thickness).

V/Q Scans are strongly recommended as the first test of choice in the assessment of the possibility of CTEPH.

Despite the improved sensitivity of CTPA scans, SPECT-V/Q imaging remains the standard for excluding CTEPH in any patient with unexplained PH.

Segmental lung perfusion defects, especially those not associated with ventilation defects (“mismatched”) are suggestive of pulmonary arterial obstruction which may indicate the presence of CTEPH (Soler et al.).

Newer SPECT imaging has better contrast and precision that standard planar V/Q scan options, and is thus recommended (Soler et al.).

The RHC is the gold standard for diagnosing PH, as it is the only method to directly and accurately measure pressure within the pulmonary artery. The two main parameters that should be assessed are mean pulmonary artery pressure (mPAP) and mean pulmonary artery wedge pressure (PAWP). Other parameters assess the severity of PH and resulting right-sided heart failure and are thus commonly measured, including right atrial pressure, cardiac output, mixed venous O2 saturation, and stroke volume index.

During RHC, some patients specifically with PAH should undergo an acute vasodilator challenge. A vasodilator challenge measures the pulmonary vasoreactivity, which is important for specifically deciding on the most effective first-line therapy of some patients with PAH.

About 10-15% of patients with idiopathic or inherited PAH respond to vasodilator testing, typically using the inhalation of nitric oxide for 10 minutes. A positive vasodilator challenge indicates that such patients may respond very well to long term high-dose calcium channel blocker therapy. If vasodilator response is NOT confirmed, patients should NOT be treated with CCBs.

Most PAH patients do not respond to the vasodilator challenge. However, these patients absolutely must still have their PAH treated, and they typically respond to available therapies with clinical and functional improvement, and improved prognosis for long-term clinical stability and improved survival. Treatment options include endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, or medications that target the prostanoid pathway.

PH is an uncommon illness and, as a result, is not widely known in the community. Patients suspected or diagnosed with PH are often quite frightened and confused about what PH means, and what is going to happen. Thus, when a patient is diagnosed with PH, it’s important to provide them and their caregivers with simple, practical, relevant information about the disease to help them come to a better understanding of the illness, the tests, and the treatments. This will help allay much of their anxiety.

Patients should be referred to a local PH expert clinic for definitive diagnostic testing and access to the best treatments available.

There are also many support and education resources available to people with PH. Useful resources from the Pulmonary Hypertension Association of Canada include:

Navigating PH - A Guide for Newly Diagnosed
The Pulse Newsletter
Connections Magazine
Toll-free Number: 1-877-774-2226

Patients should also be directed to local community PH support groups (where available).