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Cardiac temponade from harrisom

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"cardiac tamponade" AND diagnosis

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Cardiac Tamponade (Harrison's Principles of Internal Medicine, 22nd Ed.)

Definition Cardiac tamponade occurs when fluid accumulates in the pericardial space in a quantity sufficient to seriously obstruct inflow of blood into the ventricles. It can be fatal if not recognized and treated promptly.
Causes The most common causes are:
  • Idiopathic pericarditis
  • Pericarditis secondary to neoplastic disease or tuberculosis
  • Bleeding into the pericardial space from aortic dissection, cardiac surgery, trauma, or anticoagulant therapy
Notably, the volume of fluid needed to cause tamponade depends on how fast it accumulates - as little as 200 mL if it develops rapidly, versus more than 2000 mL in slowly developing effusions where the pericardium has had time to stretch and adapt.
Clinical Features
Beck's triad - the three principal features of tamponade:
  1. Hypotension
  2. Soft or absent heart sounds
  3. Jugular venous distention with a prominent x (early systolic) descent but an absent y (early diastolic) descent
Suspect tamponade in any patient with unexplained sudden enlargement of the cardiac silhouette, hypotension, and elevated jugular venous pressure. ECG clues include reduced QRS amplitude and electrical alternans of the P, QRS, or T waves.
Paradoxical pulse (pulsus paradoxus) - an important diagnostic clue: a greater-than-normal (>10 mmHg) inspiratory decline in systolic arterial pressure. This happens because both ventricles share the tight, incompressible pericardial sac - inspiratory enlargement of the right ventricle causes leftward bulging of the interventricular septum, reducing left ventricular volume, stroke volume, and systolic pressure. Note: pulsus paradoxus also occurs in about a third of constrictive pericarditis cases, and in hypovolemic shock, obstructive airway disease, and pulmonary embolism, so it isn't specific to tamponade alone.
Right ventricular infarction can mimic tamponade (hypotension, elevated JVP, slow y descent, occasional paradoxical pulse), so it belongs on the differential.
Diagnosis Because immediate treatment can be lifesaving, prompt diagnosis - usually by echocardiography - is essential:
  • Doppler shows tricuspid and pulmonic valve flow velocities increasing markedly with inspiration, while pulmonic vein, mitral, and aortic flow velocities decrease
  • Late diastolic inward motion (collapse) of the right ventricular free wall and right atrium
  • Transesophageal echo, CT, or cardiac MRI may be needed for loculated effusions
Hemodynamically, tamponade is distinguished from constrictive pericarditis and restrictive cardiomyopathy using catheterization data (Table 249-3 in the text): in tamponade, right atrial pressure is elevated with a diminished or absent y descent, unlike the prominent y descent seen in constriction.
Treatment
  • Patients with acute pericarditis should be observed frequently for effusion development; if a large effusion is present, either pericardiocentesis is performed or the patient is watched closely with serial echocardiography and pressure monitoring.
  • Pericardiocentesis is the definitive emergency treatment once tamponade manifests - via apical, parasternal, or (most commonly) subxiphoid approach, ideally under echocardiographic guidance. IV saline can be given while preparing for the procedure, but the pericardiocentesis itself must not be delayed.
  • Intrapericardial pressure should be measured before drainage, and the pericardial space should be drained as completely as possible; a catheter can be left in place for reaccumulating fluid.
  • Surgical drainage via limited subxiphoid thoracotomy may be needed for recurrent tamponade, loculated effusions, or to obtain tissue for diagnosis.
  • Pericardial fluid should be sent for cell counts, cytology, cultures, and (where relevant) TB PCR/adenosine deaminase - bloody fluid in developed nations is most often due to neoplasm, renal failure, or cardiac trauma; in developing nations, tuberculosis is also a common cause of bloody/exudative effusion.
  • Harrison's Principles of Internal Medicine, 22nd Ed., Ch. 281 (Pericardial Disease / Cardiac Tamponade)
Recent literature note: A 2024 systematic review found pulmonary hypertension may attenuate classic tamponade physiology and confound bedside diagnosis (PMID: 38622465), and a 2024 systematic review specifically characterized tamponade presentations in people living with HIV (PMID: 39210274). Neither contradicts the core Harrison's teaching above, but they add nuance for atypical populations - worth checking if your clinical scenario involves pulmonary hypertension or HIV.
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