|
|
| Line 1: |
Line 1: |
| ==Pathophysiology & Etiology==
| | #redirect:[[Cardiac tamponade]] |
| | |
| * Cardiac tamponade occurs when increasing pericardial pressure leads to decreased left ventricular volume and elevated diastolic pressures. This elevation in diastolic pressure impairs LV filling leading to diminished stroke volume and blood pressure. The transmural or distending pressure is equal to the intracavitary pressure minus the pericardial pressure. Normally, pericardial pressure is negative and the filling is favored. When pericardial pressure becomes more and more positive, the distending pressure is diminished and the chamber collapses.
| |
| * The compensatory mechanisms are aimed at maintaining perfusion and cardiac output. Over time, blood volume increases. Adrenergic stimulation leads to increased inotropy and ejection fraction as well as tachycardia and increased systemic vascular resistance.
| |
| * There are many causes of pericardial effusions with frequencies varying depending on the population studied. The major causes include infection, infarction, trauma, AIDS, malignancy, radiation, collagen vascular disease, uremia, hypothyroidism, drugs, post-CABG and others. Diagnostic pericardiocentesis has a 6% yield. If the fluid is removed therapeutically, it is diagnostic 1/3 of the time.
| |
| * In a series of 75 patients presenting to a tertiary care medical center, 25% were malignant, 27% infectious, 12% related to rheumatologic disease and 14% to radiation. AIDS has become the leading cause of pericardial effusion in many hospitals and is associated with shortened survival. Pericardial effusion is the most common initial, cardiovascular manifestation of HIV disease.
| |
| *:* Malignant effusions
| |
| *:*:* Virtually every neoplasm has been reported to metastasize to the pericardium. In a study of 789 patients with pericardial metastases, 37% were lung, 22% breast and 17% hematologic. The majority was found only at autopsy and was not clinically significant. The incidence of tamponade in those with metastatic disease to the heart is approximately 15%. Of cancer patients with effusions, 70% are malignant with only 45% being bloody at drainage. Cytology is positive in 80%, while pericardial biopsy is positive in only 55%.
| |
| * Hemodynamic Manifestations: The hallmark is equalization of diastolic pressures. PCWP, RAP, RVEDP, LVEDP and pericardial pressures equalize usually to within 1-2 mm Hg. The RAP is elevated and the pressure waveform demonstrates an accentuated x descent and an attenuated y descent. As little as 50cc of fluid can cause tamponade if accumulation is rapid, while >1500cc can drain from patients who are otherwise hemodynamically stable.
| |
| *:* Pulsus Paradoxus: A greater than normal decline in arterial systolic pressure with inspiration. The paradox refers to Kussmaul’s finding that intermittently the pulse was not palpable despite continued heart sounds. Increased right ventricular filling during inspiration and resultant interventricular septal bulging leading to impaired left ventricular filling is the most often quoted mechanism. A pulsus may be present in nontamponade disorders such as COPD, severe hypovolemic shock, RV infarction, and PE. Tamponade without pulsus paradoxus occurs in those with preexisting elevation of left or right ventricular diastolic pressures (PHTN, CHF, LVH, ASD, severe AI).
| |
| | |
| Echocardiographic findings of tamponade include seeing the effusion and evidence of RA (right atrium), RV (right ventricle) diastolic, LA (left atrium) or LV (left ventricle) collapse. As can be inferred from the pathophysiology, other finding include seeing reciprocal respiratory variations in LV and RV chamber size; increased flow across the tricuspid valve with reciprocal decrease across the mitral valve during inspiration; reduced collapse of the IVC during inspiration; and septal bulging. RV and RA collapse are the most useful findings. PTHN, RVH and TR may eliminate these findings. RV diastolic collapse occurs when the C.O. falls by about 1/5.
| |
| | |
| == Treatment ==
| |
| Tamponade presents as a spectrum of illness. There is not much debate in the treatment of the very sick or the asymptomatic patient. The debate occurs in those with echocardiographic evidence of tamponade but no clinical findings. A prudent strategy in these cases is to observe the progression of the disease process and intervene at the onset of any evidence of compromise. Volume repletion, serial echocardiographic and clinical assessment is warranted in these cases.
| |