From the Guidelines
The >50% respiratory variation in an echocardiogram is not directly mentioned in the provided evidence, however, a respiratory variation >25% over the AV-valves is mentioned as a sign of constrictive pericarditis 1. In the context of echocardiography, respiratory variation refers to the change in cardiac chamber sizes or blood flow velocities during the respiratory cycle.
- The physiological basis for this phenomenon relates to the relationship between intrathoracic pressure changes during respiration and venous return to the heart.
- During inspiration, the negative intrathoracic pressure increases the pressure gradient for blood return to the right atrium, causing changes in cardiac chamber sizes and blood flow velocities.
- This measurement should be interpreted alongside other clinical parameters and not used in isolation for clinical decision-making, especially in mechanically ventilated patients where the relationship may be reversed. The most recent and highest quality study provided is from 2015, which discusses the use of echocardiography in acute cardiovascular care 1.
- These studies highlight the importance of echocardiography in assessing cardiac morphology and hemodynamics in acute cardiovascular conditions.
- They also discuss the use of echocardiography in guiding fluid management decisions and assessing volume responsiveness in critically ill patients. However, none of these studies specifically mention a >50% respiratory variation in an echocardiogram. Therefore, based on the available evidence, it is not possible to make a definitive recommendation regarding the >50% respiratory variation in an echocardiogram. Further research is needed to fully understand the significance of this finding and its implications for patient care.
From the Research
Respiratory Variation in Echocardiogram
- The respiratory variation in echocardiogram is used to diagnose cardiac tamponade, which is a medical emergency caused by the accumulation of pericardial fluid, blood, pus, or air in the pericardium 2.
- A study compared the sensitivity, specificity, and positive predictive value of respiratory changes in transvalvular flow velocities to those of right atrial collapse and right ventricular collapse in the diagnosis of cardiac tamponade 3.
- The study found that an inspiratory decrease > 22% in the peak velocity of the early mitral flow, an inspiratory reduction > 20% in the peak velocity of the aortic flow, and an inspiratory increase > 25% in the peak velocity of the pulmonary flow were indicative of cardiac tamponade 3.
- Another study reviewed 2D and Doppler findings in patients diagnosed with effusive-constrictive pericarditis (ECP) and compared these to patients with cardiac tamponade and constrictive pericarditis (CP) 4.
- The study found that ECP may have unique echo-Doppler features that distinguish it from both CP and tamponade, including higher medial and lateral e' velocities and higher inspiratory and expiratory mitral E/A ratios compared to tamponade 4.
Diagnostic Criteria
- The diagnostic criteria for cardiac tamponade include hypotension, increased jugular venous pressure, and distant heart sounds (Beck triad) 2.
- Echocardiography is a key imaging modality used to confirm the diagnosis of cardiac tamponade, and it can also be used to guide pericardiocentesis 2.
- The respiratory variation in echocardiogram can be used to diagnose cardiac tamponade, with a > 50% respiratory variation in mitral and tricuspid flow velocities being indicative of tamponade 3.