Table 1 Comparison of constrictive pericarditis and restrictive cardiomyopathy.

	Constrictive pericarditis	Restrictive cardiomyopathy
Most common aetiology	Idiopathic	Idiopathic
	Post‐cardiac surgery
	Radiotherapy	Infiltrative; amyloidosis, eosinophilic diseases
	Connective tissue disease
	Infection/tuberculosis	Radiotherapy
	Malignancy
Clinical symptoms	Dyspnoea, fatigue, peripheral oedema, ascites	Dyspnoea, fatigue
		Peripheral oedema
Pulsus paradoxus	Uncommon	Absent
JVP height	Elevated	Elevated
JVP waveform	Prominent X and Y descents	Prominent X descent
Kussmaul's sign	Often present	Absent
Pericardial knock	Often present	Absent
ECG		Low voltage QRS complexes in amyloidosis
Atrial size	Usually normal	Dilated
LV and RV size/systolic function/2D appearance	Usually normal	Normal or mildly reduced LV systolic function
Increased LV wall thickness	Absent	May be present in infiltrative causes
Septal motion	Abnormal	Normal
Septal position	Respiratory variation	Normal
Mitral/tricuspid regurgitation	Infrequent	Frequent (TR>MR)
Mitral inflow pattern PW Doppler	Increased E velocity	Increased E velocity
	Shortened deceleration time	Restrictive filling pattern
	Mitral E/A ratio often >2.0	Mitral E/A ratio >2.0, shortened DT (<160 ms)
Respiratory variation	Exaggerated and reciprocal respiratory changes in Doppler inflows; increased right sided Doppler velocities (tricuspid, pulmonary valve) and reduced left sided Doppler velocities (mitral, aortic) with inspiration. Opposite changes occur with expiration.	Normal with minimal respiratory variation of Doppler inflows
	Percentage change from expiration to inspiration: †mitral E velocity >–25% (–33 (9)%), aortic velocity –14 (5)%, tricuspid E velocity 44 (22)%, pulmonary artery velocity 16 (4%)19	Percentage change from first beat of expiration to first beat of inspiration: †mitral E velocity –3% (4)%, tricuspid E velocity 17 (16)%, aortic velocity –4 (5)%, pulmonary artery velocity 5% (7)%19
IVRT	Duration increases from expiration to inspiration, increased respiratory variation IVRT >25% (50 (14)%)†19	Constant throughout respiration, minimal respiratory variation of IVRT duration 4 (7)%†19
Pulmonary vein PW Doppler	Increased respiratory variation of diastolic pulmonary vein Doppler flow >18%20	No significant respiratory variation
IVC	Dilated IVC	Dilated IVC
	<50% reduction in IVC width with inspiration	<50% reduction in IVC width with inspiration
Hepatic vein	Prominent diastolic flow reversals in expiration	Prominent diastolic atrial flow reversals in inspiration
SVC Doppler	Diastolic prominence of forward flow (reduced systolic forward flow)	Diastolic prominence of forward flow (reduced systolic forward flow)
Pulmonary hypertension	Rare and mild	Frequent and moderate‐severe elevation
Colour M mode propagation velocity (first aliasing contour)	Normal to increased >100 cm/s20	Reduced (<100 cm/s)20
Tissue Doppler; mitral annulus	Normal to increased E' velocity >8 cm/s20	Reduced E' velocity <8 cm/s20
CXR	Pericardial calcification	No pericardial calcification
Pericardium thickness on CT/MRI imaging	Increased	Normal
BNP	Normal to minimally elevated 128 (53) pg/ml23	Notably elevated 826 (172) pg/ml23
Catheterisation haemodynamics	Elevation and near equalisation of all diastolic pressures*	Elevation and near equalisation of all diastolic pressures*
	LVEDP‐RVEDP ⩽5 mm Hg*	LVEDP‐RVEDP >5 mmHg*
	PASP ⩽55 mm Hg*	PASP >40 mm Hg*
	RVEDP/RVSP >1/3*	RVEDP/RVSP <1/3*
	Dissociation of intracardiac and intrathoracic pressures with increased respiratory variation between the PCWP and early diastolic LV pressure gradient ⩾5 mm Hg22 (fig 3A)
	Increased ventricular interdependence; discordant changes of LV systolic pressure and RV systolic pressure with respiration22 (fig 3B)
Endomyocardial biopsy	Usually normal myocardium	Abnormal or non‐specific
Treatment	Pericardectomy	Medical treatment
		± treatment of underlying disorder
		± cardiac transplantation

BNP, B‐type natriuretic peptide; CT, computed tomography; CXR, chest x ray; ECG, electrocardiogram; IVC, inferior vena cava; IVRT, left ventricular isovolumic relaxation time; JVP, jugular venous pressure; LV, left ventricle; LVEDP, left ventricular end‐diastolic pressure; MR, mitral regurgitation; MRI, magnetic resonance imaging; PASP, pulmonary artery systolic pressure; PCWP, pulmonary capillary wedge pressure; PW, pulsed wave; RV, right ventricle; RVEDP, right ventricular end‐diastolic pressure; RVSP, right ventricular systolic pressure; SVC, superior vena cava; TR, tricuspid regurgitation.

This table presents an outline of parameters which can be useful in differentiating the above two conditions, but in the individual patient discordant data can occur, and the overall distinction should be based on an overall assessment.

*Suboptimal sensitivity and specificity of these criteria may limit the clinical usefulness in individual patients.

†Percentage change from the first beat of expiration to the first beat of inspiration. Values are presented as mean (SD). All p values are <0.05 comparing percentage respiratory change in constrictive pericarditis versus restrictive cardiomyopathy and constrictive pericarditis versus normal.¹⁹ The respiratory variation (%) represents a continuum and cut‐offs are not absolute; –% indicates a negative direction of change.