A 53-year-old man presents with lower extremity swelling, shortness of breath, and abdominal fullness. He has a past medical history of non-Hodgkin lymphoma, hypertension, and gastroesophageal reflux disease. He previously was treated with chemotherapy and radiation therapy and has been in remission for more than 10 years. Vital signs are heart rate of 110 bpm, blood pressure (BP) of 95/70 mm Hg, respiratory rate of 22 breaths/min, and 92% oxygen saturation on room air. Examination reveals distant heart tones, elevated jugular venous pressure to >15 cm, and clear lungs. There is 2+ pitting edema in the lower extremities with skin discoloration. Abdominal exam has shifting dullness and a tender, palpable liver edge. Chest radiograph shows clear lungs and mildly enlarged cardiac silhouette. Electrocardiogram has nonspecific ST/T changes with varying QRS and low voltages. Emergent bedside echocardiogram is obtained showing large, circumferential pericardial effusion with right ventricular diastolic collapse and significant variation with respiration in the mitral valve inflow velocity. A central venous catheter is placed, and the patient is taken to the cardiac catheterization lab where percutaneous pericardiocentesis is performed, with removal of 500 mL of serosanguinous-appearing fluid. BP improves to 114/82 mm Hg. Examination of the central venous pressure shows continued elevation to a mean pressure of 13 mm Hg with a change in morphology of the waveform after pericardial fluid removal.
The pericardium consists of 2 layers that surround most of the heart: the visceral pericardium, which is composed of a single layer of mesothelial cells, and the parietal pericardium, which is mostly acellular and contains collagen and elastic tissue.
Normally there is <50 mL of fluid in the pericardial space surrounding the heart.
Pericardium functions to maintain position of the heart, acts as barrier to potential infection, and is innervated with mechano- and chemoreceptors.
Etiology of pericardial pathology is wide ranging, including infectious, autoimmune, idiopathic, radiation-induced, trauma, neoplastic, and other causes.1-3
Normal
Pericardial pressure is subatmospheric and tracks with the respiratory cycle. During inspiration, negative intrathoracic pressure in the intrapleural space is transmitted to the structures within the thorax including the pericardial space and cardiac chambers.
Reduction in pericardial pressure during inspiration aids in augmenting venous return and diastolic filling in the right side of the heart.
Left-sided filling is dependent on pressure gradient from pulmonary veins (PV) to left atrium (LA)/left ventricle (LV).
Left heart filling gradient: PV – LV
Decrease in intrapleural pressure that occurs during inspiration is better transmitted to the venous system (PVs) than to the left heart; thus, on inspiration, left heart filling pressure is decreased, reducing left heart filling:
During inspiration: PV ↓↓ − LV ↓
Gradient is reduced, lowering filling pressure
Normal pressure-volume curve of the pericardium is steep, such that small increases in volume result in rapid increases in pressure in the intrapericardial space. In chronic fluid overload, the curve is shifted more flat and to the right, such that changes in volume have less impact on pericardial pressures.4
Relatively small volumes of rapidly accumulating fluid can cause tamponade.
Slowly accumulating effusion can become quite large without tamponade physiology.
Enhanced ventricular interdependence
The left and right heart share a common septum that is normally compliant.
During conditions where the pericardium is limited in its distensibility (eg, pericardial effusion, constrictive pericarditis), increased filling of 1 side of the heart results in decreased filling on the opposite side. This is termed enhanced ventricular interdependence (Figure 4-1) and results in discordant changes in right and LV filling, stroke volume, and systolic pressure (ie, as right-sided filling stroke volume increases, left-sided measures decrease).
Cardiac tamponade
In the early stages of tamponade, cardiac output is maintained via several mechanisms.
Increased venous return helps to maintain filling pressures and prevent diastolic collapse from the increased pericardial pressure (elevated right atrial [RA] pressure and jugular venous pressure).
Increased adrenergic tone increases heart rate and contractility.
During tamponade, elevated pericardial pressure results in impaired diastolic filling and diastolic equalization in all cardiac chambers.
As pericardial pressure continues to rise, there is progressive impairment of atrial emptying and ventricular filling (Figure 4-2); this results in a blunted y wave on the RA pressure tracing as well as right atrial and right ventricular diastolic collapse seen on echocardiography (Figure 4-3).
Surrounding pericardial fluid limiting distension results in enhanced ventricular interdependence; inspiratory increase in right heart filling results in exaggerated decrease in left heart filling.
Decreased left heart diastolic filling during inspiration results in reduced LV stroke volume and systemic arterial pressure.
Pulsus paradoxus (>10 mm Hg drop in systolic BP during inspiration). This is really an exaggeration of the normal drop in systemic blood pressure during inspiration rather than truly a paradox.
Constrictive pericarditis
Similar to cardiac tamponade, there is enhanced ventricular interdependence (increased right ventricular [RV] filling leads to decreased LV filling and vice versa) and impaired diastolic filling in constrictive physiology.
Diastolic pressure equalization occurs in all cardiac chambers.
Ventricular filling occurs during early diastole before abruptly stopping due to reaching volume limit from stiffened pericardium. This results in the characteristic “square-root” or “dip and plateau” pattern on ventricular pressure tracings (Figure 4-4).
RA pressure tracing has exaggerated y wave, resulting in “M” or “W” appearance of the RA pressure tracing (contrary to tamponade with blunted y wave) (Figure 4-5).
There is inspiratory increase in RA pressure (Kussmaul sign).
Effusive-constrictive pericarditis
Combination of tamponade and constrictive physiology.
Drainage of pericardial fluid and relief tamponade do not lower RA pressure.
Unmasking of hemodynamic features of constriction including prominent y descent on RA tracing and “dip and plateau” on RV tracing.
Comparing tamponade and constrictive pericarditis
Both display ventricular interdependence; however, this more pronounced in tamponade due to “coupled constraint,” where uniform liquid pressure surrounds the heart, versus “uncoupled constraint” (seen in constrictive pericarditis), where there is a more pronounced effect on thin-walled RV (leads to Kussmaul sign).
Nearly all tamponade patients have pulsus paradoxus versus only approximately one-third of constrictive pericarditis patients.
In constriction, the fibrous pericardial tissue “insulates” cardiac chambers from changes in intrathoracic respiratory pressure changes. This is termed intrathoracic-intracardiac dissociation.
Measured by change in pulmonary capillary wedge pressure (PCWP)–LV end-diastolic pressure (LVEDP) gradient with respiration of >5 mm Hg
RA waveform
Tamponade with blunted y descent
Constriction with exaggerated y descent (“M” or “W” pattern)
Differentiating constrictive pericarditis from restrictive cardiomyopathy
This is very important because treatment modality (ie, pericardiectomy) is a potentially curative but high-risk procedure, and clinically, it can be difficult to distinguish between constrictive pericarditis and restrictive cardiomyopathy by symptoms and exam.
Classically, features suggesting constrictive pericarditis include:
RV systolic pressure (RVSP) <55 mm Hg
Equalization of diastolic pressures (LVEDP – RV end-diastolic pressure [RVEDP] <5 mm Hg)
RVEDP/RVSP ratio >⅓
Square-root sign
Dynamic findings of enhanced ventricular interdependence and intracardiac-intraventricular dissociation showed better discrimination (specificity) than classical findings.5
Magnetic resonance imaging and computed tomography findings with thickened pericardium may suggest constrictive process when thickened pericardium is demonstrated.6
This is not absolute because a restrictive process can still be present, and constriction can occur with normal width pericardium.
Endomyocardial biopsy can be helpful in diagnosing restrictive cardiomyopathy.
Echo Doppler parameters are available to further help distinguish these conditions.7-11
Given the diagnostic challenge and high stakes related to substantial procedure, a comprehensive approach integrating history, invasive assessment, and imaging is paramount.
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