The diagnosis of pulmonary heart disease is not easy as both lung and heart disease can produce similar symptoms. Therefore, the differential diagnosis should assess:

Among the investigations available to determine cor pulmonale are:

- Chest x-ray – right ventricular hypertrophy, right atrial dilatation, prominent pulmonary artery

- ECG – right ventricular hypertrophy, dysrhythmia, P pulmonale (characteristic peaked P wave)

- Thrombophilia screen- to detect chronic venous thromboembolism (proteins C and S, antithrombin III, homocysteine levels)

If heart disease and lung disease have been excluded, a ventilation/perfusion scan is performed to rule out CTEPH. If unmatched perfusion defects are found, further evaluation by CT pulmonary angiography, right heart catheterization, and selective pulmonary angiography is performed.

If the echocardiogram is compatible with a diagnosis of pulmonary hypertension, common causes of pulmonary hypertension (left heart disease and lung disease) are considered and further tests are performed accordingly. These tests generally include electrocardiography (ECG), pulmonary function tests including lung diffusion capacity for carbon monoxide and arterial blood gas measurements, X-rays of the chest and high-resolution computed tomography (CT) scanning.

Early diagnosis still remains a challenge in CTEPH, with a median time of 14 months between symptom onset and diagnosis in expert centres. A suspicion of PH is often raised by echocardiography, but an invasive right heart catheterisation is required to confirm it. Once PH is diagnosed, the presence of thromboembolic disease requires imaging. The recommended diagnostic algorithm stresses the importance of initial investigation using an echocardiogram and V/Q scan and confirmation with right heart catheter and pulmonary angiography (PA).

Both V/Q scanning and modern multidetector CT angiography (CTPA) may be accurate methods for the detection of CTEPH, with excellent diagnostic efficacy in expert hands (sensitivity, specificity, and accuracy of 100%, 93.7%, and 96.5% for V/Q and 96.1%, 95.2%, and 95.6% for CTPA). However, CTPA alone cannot exclude the disease, but may help identify pulmonary artery distension resulting in left main coronary artery compression, pulmonary parenchymal lesions (e.g. as complications from previous pulmonary infarctions), and bleeding from bronchial collateral arteries. Today, the gold standard imaging remains invasive pulmonary angiography (PAG) using native angiograms or a digital subtraction technique.

The pulmonary embolism rule-out criteria (PERC) helps assess people in whom pulmonary embolism is suspected, but unlikely. Unlike the Wells score and Geneva score, which are clinical prediction rules intended to risk stratify people with suspected PE, the PERC rule is designed to rule out risk of PE in people when the physician has already stratified them into a low-risk category.

People in this low risk category without any of these criteria may undergo no further diagnostic testing for PE: Hypoxia — Sa 50, hormone use, tachycardia. The rationale behind this decision is that further testing (specifically CT angiogram of the chest) may cause more harm (from radiation exposure and contrast dye) than the risk of PE. The PERC rule has a sensitivity of 97.4% and specificity of 21.9% with a false negative rate of 1.0% (16/1666).

In people with a low or moderate suspicion of PE, a normal D-dimer level (shown in a blood test) is enough to exclude the possibility of thrombotic PE, with a three-month risk of thromboembolic events being 0.14%. D-dimer is highly sensitive but not specific (specificity around 50%). In other words, a positive D-dimer is not synonymous with PE, but a negative D-dimer is, with a good degree of certainty, an indication of absence of a PE. The typical cut off is 500 μg/L, although this varies based on the assay. However, in those over the age of 50, changing the cut-off value to the person's age multiplied by 10 μg/L (accounting for assay which has been used) is recommended as it decreases the number of falsely positive tests without missing any additional cases of PE.

When a PE is being suspected, several blood tests are done in order to exclude important secondary causes of PE. This includes a full blood count, clotting status (PT, aPTT, TT), and some screening tests (erythrocyte sedimentation rate, renal function, liver enzymes, electrolytes). If one of these is abnormal, further investigations might be warranted.

Troponin levels are increased in between 16–47% with pulmonary embolism.

Blood tests routinely performed include electrolytes (sodium, potassium), measures of kidney function, liver function tests, thyroid function tests, a complete blood count, and often C-reactive protein if infection is suspected. An elevated B-type natriuretic peptide (BNP) is a specific test indicative of heart failure. Additionally, BNP can be used to differentiate between causes of dyspnea due to heart failure from other causes of dyspnea. If myocardial infarction is suspected, various cardiac markers may be used.

According to a meta-analysis comparing BNP and N-terminal pro-BNP (NTproBNP) in the diagnosis of heart failure, BNP is a better indicator for heart failure and left ventricular systolic dysfunction. In groups of symptomatic patients, a diagnostic odds ratio of 27 for BNP compares with a sensitivity of 85% and specificity of 84% in detecting heart failure.

No system of diagnostic criteria has been agreed on as the gold standard for heart failure. The National Institute for Health and Care Excellence recommends measuring brain natriuretic peptide (BNP) followed by ultrasound of the heart if positive. This is recommended in those with shortness of breath. In those with heart failure who worsen both a BNP and a troponin are recommended to help determine likely outcomes.

Historically the prognosis for patients with untreated CTEPH was poor, with a 5-year survival of 40 mmHg at presentation. More contemporary data from the European CTEPH registry have demonstrated a 70% 3-year survival in patients with CTEPH who do not undergo the surgical procedure of pulmonary endarterectomy (PEA). Recent data from an international CTEPH registry demonstrate that mortality in CTEPH is associated with New York Heart Association (NYHA) functional class IV, increased right atrial pressure, and a history of cancer. Furthermore, comorbidities such as coronary disease, left heart failure, and chronic obstructive pulmonary disease (COPD) are risk factors for mortality.

COPD may need to be differentiated from other causes of shortness of breath such as congestive heart failure, pulmonary embolism, pneumonia, or pneumothorax. Many people with COPD mistakenly think they have asthma. The distinction between asthma and COPD is made on the basis of the symptoms, smoking history, and whether airflow limitation is reversible with bronchodilators at spirometry. Tuberculosis may also present with a chronic cough and should be considered in locations where it is common. Less common conditions that may present similarly include bronchopulmonary dysplasia and obliterative bronchiolitis. Chronic bronchitis may occur with normal airflow and in this situation it is not classified as COPD.

A chest X-ray and complete blood count may be useful to exclude other conditions at the time of diagnosis. Characteristic signs on X-ray are overexpanded lungs, a flattened diaphragm, increased retrosternal airspace, and bullae, while it can help exclude other lung diseases, such as pneumonia, pulmonary edema, or a pneumothorax. A high-resolution computed tomography scan of the chest may show the distribution of emphysema throughout the lungs and can also be useful to exclude other lung diseases. Unless surgery is planned, however, this rarely affects management. An analysis of arterial blood is used to determine the need for oxygen; this is recommended in those with an FEV less than 35% predicted, those with a peripheral oxygen saturation less than 92%, and those with symptoms of congestive heart failure. In areas of the world where alpha-1 antitrypsin deficiency is common, people with COPD (particularly those below the age of 45 and with emphysema affecting the lower parts of the lungs) should be considered for testing.

The epidemiology of pulmonary heart disease (cor pulmonale) accounts for 7% of all heart disease in the U.S. According to Weitzenblum, et al., the mortality that is related to cor pulmonale is not easy to ascertain, as it is a complication of COPD.

A jugular venous distension is the most sensitive clinical sign for acute decompensation.

The diagnosis can be confirmed by lung biopsy. A videoscopic assisted thoracoscopic wedge biopsy (VATS) under general anesthesia may be necessary to obtain enough tissue to make an accurate diagnosis. This kind of biopsy involves placement of several tubes through the chest wall, one of which is used to cut off a piece of lung to send for evaluation. The removed tissue is examined histopathologically by microscopy to confirm the presence and pattern of fibrosis as well as presence of other features that may indicate a specific cause e.g. specific types of mineral dust or possible response to therapy e.g. a pattern of so-called non-specific interstitial fibrosis.

Misdiagnosis is common because, while overall pulmonary fibrosis is not rare, each individual type of pulmonary fibrosis is uncommon and the evaluation of patients with these diseases is complex and requires a multidisciplinary approach. Terminology has been standardized but difficulties still exist in their application. Even experts may disagree with the classification of some cases.

On spirometry, as a restrictive lung disease, both the FEV1 (forced expiratory volume in 1 second) and FVC (forced vital capacity) are reduced so the FEV1/FVC ratio is normal or even increased in contrast to obstructive lung disease where this ratio is reduced. The values for residual volume and total lung capacity are generally decreased in restrictive lung disease.

The diagnosis of portopulmonary hypertension is based on hemodynamic criteria:

1. . Portal hypertension and/or liver disease (clinical diagnosis—ascites/varices/splenomegaly)

2. . Mean pulmonary artery pressure—MPAP > 25 mmHg at rest

3. . Pulmonary vascular resistance—PVR > 240 dynes s cm−5

4. . Pulmonary artery occlusion pressure— PAOP 12 mmHg where TPG = MPAP − PAOP.

The diagnosis is usually first suggested by a transthoracic echocardiogram, part of the standard pre-transplantation work-up. Echocardiogram estimated pulmonary artery systolic pressures of 40 to 50 mm Hg are used as a screening cutoff for PPH diagnosis, with a sensitivity of 100% and a specificity as high as 96%. The negative predictive value of this method is 100% but the positive predictive value is 60%. Thereafter, these patients are referred for pulmonary artery catheterization.

The limitations of echocardiography are related to the derivative nature of non-invasive PAP estimation. The measurement of PAP by echocardiogram is made using a simplified Bernoulli equation. High cardiac index and pulmonary capillary wedge pressures, however, may lead to false positives by this standard. By one institution’s evaluation, the correlation between estimated systolic PAP and directly measured PAP was poor, 0.49. For these reasons, right heart catheterization is needed to confirm the diagnosis.

The medical care of patients with hypertensive heart disease falls under 2 categories—

- Treatment of hypertension

- Prevention (and, if present, treatment) of heart failure or other cardiovascular disease

According to JNC 7, BP goals should be as follows :

- Less than 140/90mm Hg in patients with uncomplicated hypertension

- Less than 130/85mm Hg in patients with diabetes and those with renal disease with less than 1g/24-hour proteinuria

- Less than 125/75mm Hg in patients with renal disease and more than 1 g/24-hour proteinuria

Pulmonary veno-occlusive disease can only be well diagnosed with a lung biopsy. CT scans may show characteristic findings such as ground-glass opacities in centrilobular distribution, and mediastinal lymphadenopathy, but these findings are non-specific and may be seen in other conditions. However, pulmonary hypertension (revealed via physical examination), in the presence of pleural effusion (done via CT scan) usually indicates a diagnosis of pulmonary veno-occlusive disease. The prognosis indicates usually a 2-year (24 month) life expectancy after diagnosis.

Supplemental oxygen may be administered if blood levels of oxygen are low; the Heart Failure Society of America, however, has recommended that it not be used routinely.

Spirometry classically reveals a reduction in the vital capacity (VC) with either a proportionate reduction in airflows, or increased airflows for the observed vital capacity. The latter finding reflects the increased lung stiffness (reduced lung compliance) associated with pulmonary fibrosis, which leads to increased lung elastic recoil.

Measurement of static lung volumes using body plethysmography or other techniques typically reveals reduced lung volumes (restriction). This reflects the difficulty encountered in inflating the fibrotic lungs.

The diffusing capacity for carbon monoxide (DL) is invariably reduced in IPF and may be the only abnormality in mild or early disease. Its impairment underlies the propensity of patients with IPF to exhibit oxygen desaturation with exercise which can also be evaluated using the 6-minute walk test (6MWT).

Terms such as ‘mild’, ‘moderate’, and ‘severe’ are sometimes used for staging disease and are commonly based on resting pulmonary function test measurements. However, there is no clear consensus regarding the staging of IPF patients and what are the best criteria and values to use. Mild-to-moderate IPF has been characterized by the following functional criteria:

- Forced Vital Capacity (FVC) of ≥50%

- DL of ≥30%

- 6MWT distance ≥150 meters.

Bronchoalveolar lavage (BAL) is a well-tolerated diagnostic procedure in ILD. BAL cytology analyses (differential cell counts) should be considered in the evaluation of patients with IPF at the discretion of the treating physician based on availability and experience at their institution. BAL may reveal alternative specific diagnoses: malignancy, infections, eosinophilic pneumonia, histiocytosis X, or alveolar proteinosis. In the evaluation of patients with suspected IPF, the most important application of BAL is in the exclusion of other diagnoses. Prominent lymphocytosis (>30%) generally allows excluding a diagnosis of IPF.

Respiratory diseases may be investigated by performing one or more of the following tests

- Biopsy of the lung or pleura

- Blood test

- Bronchoscopy

- Chest x-ray

- Computed tomography scan, including high-resolution computed tomography

- Culture of microorganisms from secretions such as sputum

- Ultrasound scanning can be useful to detect fluid such as pleural effusion

- Pulmonary function test

- Ventilation—perfusion scan

There is no one single test for confirming that breathlessness is caused by pulmonary edema; indeed, in many cases, the cause of shortness of breath is probably multifactorial.

Low oxygen saturation and disturbed arterial blood gas readings support the proposed diagnosis by suggesting a pulmonary shunt. Chest X-ray will show fluid in the alveolar walls, Kerley B lines, increased vascular shadowing in a classical batwing peri-hilum pattern, upper lobe diversion (increased blood flow to the superior parts of the lung), and possibly pleural effusions. In contrast, patchy alveolar infiltrates are more typically associated with noncardiogenic edema

Lung ultrasound, employed by a healthcare provider at the point of care, is also a useful tool to diagnose pulmonary edema; not only is it accurate, but it may quantify the degree of lung water, track changes over time, and differentiate between cardiogenic and non-cardiogenic edema.

Especially in the case of cardiogenic pulmonary edema, urgent echocardiography may strengthen the diagnosis by demonstrating impaired left ventricular function, high central venous pressures and high pulmonary artery pressures.

Blood tests are performed for electrolytes (sodium, potassium) and markers of renal function (creatinine, urea). Liver enzymes, inflammatory markers (usually C-reactive protein) and a complete blood count as well as coagulation studies (PT, aPTT) are also typically requested. B-type natriuretic peptide (BNP) is available in many hospitals, sometimes even as a point-of-care test. Low levels of BNP (<100 pg/ml) suggest a cardiac cause is unlikely.

For some types of chILD and few forms adult ILD genetic causes have been identified. These may be identified by blood tests. For a limited number of cases this is a definite advantage, as a precise molecular diagnosis can be done; frequently then there is no need for a lung biopsy. Testing is available for

The hepatopulmonary syndrome is suspected in any patient with known liver disease who reports dyspnea (particularly platypnea). Patients with clinically significant symptoms should undergo pulse oximetry. If the syndrome is advanced, arterial blood gasses should be measured on air.

A useful diagnostic test is contrast echocardiography. Intravenous microbubbles (> 10 micrometers in diameter) from agitated normal saline that are normally obstructed by pulmonary capillaries (normally <8 to 15 micrometers) rapidly transit the lung and appear in the left atrium of the heart within 7 heart beats. Similarly, intravenous technetium (99mTc) albumin aggregated may transit the lungs and appear in the kidney and brain. Pulmonary angiography may reveal diffusely fine or blotchy vascular configuration. The distinction has to be made with an intracardiac right-to-left shunt.