Stress Echocardiography

Here is a quick tip about stress echocardiography. During stress echocardiography, both left ventricular dilatation and decline in global systolic function are indicative for severe coronary artery disease. Both are less common to occur with dobutamine stress echo rather than exercise echocardiography. However, hypotension is also a marker of severe coronary artery disease that is more likely to occur during dobutamine stress echocardiography. his may be due to the vasodialtor effect of dobutamine or due to dynamic left ventricular outflow tract obstruction with increased contractility.

Is oxygen beneficial in patients with myocardial infarction?

In classic teaching in medical school, we were told to give supplemental oxygen to patients with myocardial infarction. But in the era of evidence based medicine this may be not true for everyone. The AVOID trial has addressed tis issue. The AVOID investigators has found that oxygen in the non-hypoxic STEMI patients was associated with increased infarction size (detected by CMR), increased rate of re-infarction and increased incidence of ventricular arrhythmias. So, it is not recommended to give supplemental oxygen if the patient is not hypoxic on room-air, i.e. the patient has SO2 above 94%. This may be explained by the increased formation of oxygen free radicles that are associated with more myocardial injury (chemical rather than ischemic).

This is a link to the AVOID study results.

Tips on echocardiography for constrictive pericarditis

•  Echocardiographic features of constrictive pericarditis include:

               - Septal bounce

               - dilated IVC

               - dilated hepatic veins with diastolic flow reversal on expiration

               - absence of normal sliding motion between the RV and the liver

               - respiratory varitions of mitral E velocity with more than 25% increase with expiration 

• Respiratory variations of mitral inflow (E-wave) is not always present in constrictive pericarditis. It can be masked by increased left ventricular end diastolic pressure. However, it can be unmasked by imaging in the sitting up position. Also some diuretics may unmask it. Howeverm its absence does not exclude constriction.

•  Respiratory variations of mitral E-wave velocity can occur also with COPD. in cases of COPD, the highest E-wave is at onset of expiration, while in constriction, the highest E-wave is at end expiration. Another useful tip, use SVC flow to differentiate COPD from constriction. In COPD SVC systolic flow increases markedly with inspiration. But in case of constriction, SVC diastolic flow shows limited increase with inspiration (less than 20cm/sec).

• Using Tissue Doppler Imaging to differentiate constriction from restriction:

               - medial mitral e' velocity less than 8 cm/sec is associated with restriction.

               - constriction is associated with "Annulus Reversus" on TDI. This means that the medial annular e' velocity is higher than that of lateral annulus. Normally, the lateral mitral annular e' velocity is higher than the medial by more than 20%. This annulus reversus disappears after pericardiectomy.

ECG tips in acute coronary syndromes

•  Wellens' syndrome: This is characterized by symmetrical T-wave inversion in the precordial leads during the chest pain free periods in the setting of ACS. This occurs without Q waves,o  ST-elevation. The cardiac enzymes are not or minimally elevated. During the chest pain episoes, this T-wave inversion may be normalized (pseudonormalization). The presence of Weelens' syndrome indicates the presence of critical lesion in the proximal segment of the left anterior descending artery (LAD). Early intervention is advised in this settings.

• De Winter's T waves: This is charachterized by an upsloping ST depression (>1mm at J point) followed by a tall symmetric T-wave. This was present in precordial leads. It is associated with 0.5-1 mm elevation in aVR. This pattern is present in 2% of anterior MI. It may precede or follow the usual pattern of anterior STEMI. It was associated with LAD occlusion. Presence of this sign should prompt activation of cathlab immediately.

• aVR - Does it have any diagnostic value? 

Actually it has. In the setting of diffuse ST-depression (more than 7 of the other11 leads), ST elevation in the aVR indicates the presence of either left main coronary stenosis or multivessel disease.

•  Localization of the culprit leion in the setting of inferior STEMI: You may compare the amplitude of ST-segment elevation in the inferior leads. If the highest elevation is in the lead II, LCX occlusion is expected. If lead III shows the highest ST-segment elevation, RCA occlusion is more common.

• Acute MI with LBBB: We all know that LBBB causes changes in ST-segment, rendering the diagnosis of STEMI difficult. some useful tips are presented here. Actually new LBBB in the setting of STEMI is the result of proximal total occlusion of LAD or left main coronary artery occlusion. These are sites of obstruction before the 1st septal branch that supplies the left bundle branch. An infarction due to occlusion in this site is usually associated with severe pain and hemodynamic compromise due to large area of infarction involved. Those patients may present with acute heart failure or cardiogenic shock. The interpretation of ECG with understanding this clinical tips is somewhat helpful in making the diagnosis. Another point is the Sgarbossa diagnostic criteria.  

concordant ST elevation >1mm is given 5 points. Concordant ST depression >1mm is given 3 points. Discordant ST elevation >5mm is given 2 points. The higher the Sgarbossa score the patient hasm the more likely he has a myocardial infarction. However, Dr. Smith has found some modification on these criteria to be more useful. He suugested that the discordant ST elevation to be considered positive if it reaches >25% of the depth of the preceding S wave.

•  After coronary reprefusion we should monitor for the signs of myocardial reperfusion, one of which is reperfusion arrhythmias. The most specific arrhythmia for reperfusion is accelerated idioventricular rhythm, also known as slow VT. It is a ventricular rhythm at rate of 60-120 bpm.