Heart Failure Diagnosis and Investigation

See also: Heart Failure Management.

Acute and chronic

Heart failure has traditionally been described as acute or chronic, but this can be confusing and should be used to describe time, rather than severity. New onset (first presentation with acute or slow onset), transient (recurrent or episodic) and chronic (persistent whether stable, worsening or decompensated) heart failure may be a more useful classification.

Systolic and diastolic

Similarly, a distinction is frequently made between systolic and diastolic heart failure. This is somewhat arbitrary and many patients with heart failure have evidence of both. Left ventricular systolic dysfunction (LVSD), usually defined as an LV ejection fraction < 40% on echocardiography.
Some symptomatic patients have a normal ejection fraction and no obvious cause for increased myocardial demand. This condition has been variously termed diastolic heart failure, heart failure with preserved LV function, heart failure with a normal ejection fraction (HFNEF) or heart failure with preserved systolic function (HFPSF).²

High and low output

Certain medical conditions (see below) increase demands on cardiac output, causing a clinical picture of heart failure and this is known as high output cardiac failure. The primary abnormality is not the heart and the heart failure is reversible with treatment. Low output failure is where cardiac output is inadequate to perfuse the body (i.e. ejection fraction < 40%), or can only be adequate with high filling pressures.

Europewide:¹

• Prevalence of asymptomatic ventricular dysfunction is approximately 4%.
• Prevalence of heart failure is between 2-4% in the general population, increasing significantly with age to between 10-20% in the over-75s.
• In younger age groups, heart failure is more common in men because of the earlier onset of IHD.
• Prevalence is increasing due to aging populations and improved survival after coronary events and secondary prevention.

A UK survey of heart failure management in general practice found an average prevalence of 8.3 per 1,000 population.³

• Valve heart disease - approximately 10% of cases.
  • Aortic stenosis can cause left ventricular hypertrophy due to chronic excessive afterload.
  • Aortic or mitral regurgitation, ASD, VSD and tricuspid incompetence cause excessive preload.
• Heart failure secondary to myocardial disease:¹
  • Coronary heart disease (myocardial infarction (MI) and ischaemia, arrhythmias, e.g. atrial fibrillation, heart block)
  • Hypertension (increased vascular resistance, often with left ventricular hypertrophy but preserved ejection fraction)
  • Cardiomyopathies
  • Drugs (e.g. beta-blockers, calcium antagonists, anti-arrhythmics, cytotoxics)
  • Toxins (e.g.alcohol, cocaine, mercury, cobalt, arsenic)
  • Endocrine (diabetes, hypothyroidism, hyperthyroidism, Cushing's syndrome, adrenal insufficiency, excessive growth hormone, phaeochromocytoma)
  • Nutritional (e.g. deficiencies of thiamine, selenium, carnitine, and obesity, cachexia)
  • Infiltrative (e.g. sarcoidosis, amyloidosis, haemochromatosis, Löffler's eosinophilia, connective tissue disease)
  • Infective (e.g. Chagas' disease, HIV)
• High-output failure
  This occurs when cardiac output is normal or increased in the face of much increased needs. It can occur with a normal heart, but even earlier if there is heart disease.
  Causes include:
  • Anaemia
  • Pregnancy
  • Hyperthyroidism
  • Paget's disease of bone
  • Arteriovenous malformations
  • Beriberi

Coronary heart disease and hypertension are the most common causes of heart failure. In the UK general practice population, about 47% of men have coronary artery disease causing their heart failure, and in 46% of women hypertension is the cause.³

In general the heart fails as a whole, but sometimes a disproportionate burden falls on one ventricle, and this influences the pattern of symptoms and signs. There is no symptom or sign that is both sensitive and specific for chronic heart failure.⁴

Symptoms

• Dyspnoea and fatigue (may limit exercise tolerance).
• Fluid retention (may cause pulmonary or peripheral oedema).
• Patients do not necessarily have both, and either may dominate at any one time. In addition, patients may be depressed or complain of drug-related side-effects.
• When the left ventricle is failing (LVF): dyspnoea, poor exercise tolerance, fatigue, orthopnoea, paroxysmal nocturnal dyspnoea (PND), nocturnal cough (± pink frothy sputum) or wheeze, nocturia, cold peripheries, weight loss and muscle wasting.
• Right ventricular failure: (RVF) peripheral oedema (up to thighs, sacrum, abdominal wall), abdominal distension (ascites), nausea, anorexia, facial engorgement, pulsation in neck and face (tricuspid regurgitation), epistaxis.

Signs

• The patient may look ill and exhausted, with tachypnoea, cool peripheries, peripheral ± central cyanosis.
• There may be a tachycardia at rest, low systolic BP, a displaced apex (LV dilatation) or RV heave (pulmonary hypertension), a narrow pulse pressure or pulsus alternans (alternating large and small pulse pressures)⁵ and a raised JVP.
• On auscultation there may be a gallop rhythm due to presence of S₃ (see heart sounds) or murmurs of mitral or aortic valve disease; bilateral basal end-inspiratory crackles ± wheeze ("cardiac asthma"), pleural effusions, tender hepatomegaly – pulsatile in tricuspid regurgitation, with ascites and often extensive peripheral oedema.⁶
• The peak expiratory flow rate may be reduced but, if it is < 150 litres/min, suspect COPD or asthma.

Where there is clinical suspicion of heart failure, further investigations are required to confirm or rule out the diagnosis. They tend to be most sensitive in those patients with heart failure and reduced ejection fraction, whilst diagnostic findings may be more limited in patients with HFPEF.
Echocardiography remains the key investigation for evaluating systolic and diastolic function, but ECG and/or natriuretic proteins may enable some selection as to whom requires such testing.

• Blood tests: FBC, U&E and creatinine, LFT's, glucose, fasting lipids, thyroid function tests; consider cardiac enzymes if an MI is possible in the last few days.
• 12-lead ECG: this may elucidate the cause of heart failure (e.g. sinus tachycardia or bradycardia, SVT/AF, Q waves suggesting previous MI; also look for ischaemic ST changes, bundle branch block, atrial fibrillation, left axis deviation, and ventricular hypertrophy). An abnormal ECG has little predictive value for heart failure but a normal ECG makes LVSD unlikely (negative predictive value of 98%).⁷
• Natriuretic peptides
  • B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-proBNP) are released into the blood when the myocardium is stressed and they are advocated as useful biomarkers for the diagnosis, staging and monitoring of heart failure
  • A normal concentration (BNP < 100 pg/ml, NT-proBNP < 400 pg/ml) in an untreated patient makes heart failure an unlikely cause of symptoms whilst high concentrations (BNP > 400 pg/ml, NT-proBNP > 2000 pg/ml) make chronic heart failure likely¹
  • This may be useful in primary care to exclude patients who do not require echocardiogram⁸ or for screening high-risk groups, but provision of primary care natriuretic protein testing remains patchy
  • One primary care study identified a significant percentage of patients with ventricular dysfunction who were either asymptomatic or had mild breathlessness only from a high-risk group (> 65 years with diabetes or IHD) based on persistently high BNP⁹
  • Natriuretic peptide levels may also be elevated in other conditions such as chronic hypoxaemia, renal dysfunction, advanced age, liver cirrhosis and sepsis
• Chest X-ray (CXR) - provides supportive evidence for heart failure and helps to exclude other potential causes of breathlessness. Typical findings in heart failure include:
  • Cardiomegaly (cardiothoracic ratio > 50%)
  • Ventricular hypertrophy
  • Prominent upper lobe veins (upper lobe diversion)
  • Peribronchial cuffing
  • Diffuse interstitial or alveolar shadowing - classical perihilar "bat's wings" or nodular (especially with pre-existing COPD)
  • Fluid in the fissures
  • Pleural effusions
  • Kerley B lines
  Apart from pulmonary congestion, CXR findings are only predictive of heart failure where there are co-existing typical signs and symptoms.
• Echocardiography is the key test to provide a semi-objective assessment of cardiac function. It enables an assessment of:
  • Overall left ventricular systolic function
  • Diastolic function (necessary to diagnose HFPEF)
  • Left ventricular wall thickness
  • Valvular disease
  • Estimation of pulmonary artery systolic pressure
  It is increasingly available "open access" to GPs and should be performed in almost all patients with symptoms or signs of heart failure - SIGN guidelines state that all patients with suspected heart failure should have an echocardiogram 'if at all possible'. ⁴
• Additional tests:
  • Consider 24-hr ECG to detect paroxysmal arrhythmias
  • Cardiac magnetic resonance imaging - gold standard for assessing ventricular volumes, mass and wall motion. It can be used with contrast to identify inflammation, infiltration and scarring of the myocardium. Its use is limited by availability and cost
  • Exercise testing, CT angiography or coronary angiography are not part of routine diagnosis of heart failure but may be considered where IHD is suspected
  • Radionuclide imaging may be helpful to assess global ventricular function when echocardiography is not possible
  • Endomyocardial biopsy is rarely needed

Functional capacity may be assessed using a standardised exercise test such as the 6-minute walk test (which strongly and independently predicts morbidity and mortality in patients with left ventricular dysfunction).¹⁰ Most patients do not show a linear deterioration, but may fluctuate even in the absence of treatment changes, and changes in treatment may make things better, or worse, in the absence of measurable changes in ventricular function.
The New York Heart Association (NYHA) Classification of Heart Failure has provided a clinically useful, functional classification, outlined below:

• Prognosis is poor on the whole, with 5-year mortality varying from 26–75%.¹¹
• Heart failure accounts for at least 5% of medical hospital admissions in the UK and up to 16% of patients are back in hospital within 6 months of their first admission.
• When patients present with acute pulmonary oedema their prognosis is poorer; survival rates are predicted by severity. In those presenting with cardiogenic shock (hypotension with systolic BP < 90 mmHg, oliguria and low cardiac output), hospital mortality can be as high as 90%.

The term 'heart failure' is so absolute that alternatives such as' impairment' or 'damage' may be preferred, but the risk is that some patients may feel patronised and it is reminiscent of times when the word 'cancer' was avoided whilst talking to patients. Explaining that the heart is not pumping as strongly as it should is understood by nearly all patients, and is a good starting point from which to elaborate and give further information as required. As ever, know your patient and communicate accordingly.