A 70 year old man is admitted with shortness of breath and respiratory failure to the intensive care unit. A systolic murmur is audible on examination. A chest X-Ray reveals upper lobe diversion of pulmonary veins. A transthoracic echo reveals the following (abnormal values marked with an asterisk).
OBSERVATIONS:
TRICUSPID VALVE: Normal
PULMONIC VALVE: Normal
RIGHT VENTRICLE: Normal size and function
RIGHT ATRIUM / IVC: Normal
MITRAL VALVE: Normal
*LEFT VENTRICULAR EVALUATION:
Normal LV size. Moderate to severe impairment of systolic function. EF 25%. No regional wall motion abnormalities. Moderate LV hypertrophy.
*LEFT ATRIUM: Mildly enlarged.
*AORTIC VALVE: Thickened and calcified, with reduced opening. No aortic regurgitation.
|
Aortic valve area Left ventricular outflow tract: |
0.68cm2 0.55 m/s; |
(2 – 4) (0.8 – 1.2) |
|
Maximum velocity |
8.58 cm; |
|
|
Aortic valve Maximum velocity |
2.93 m/s; |
(<2.0) |
|
Velocity time integral (VTI) |
43 cm; |
|
|
Max pressure gradient Mean pressure gradient |
34 mm Hg 18 mm Hg |
(<16) (<10) |
|
Dimensionless severity index (DSI) |
0.19 |
a) Based on the above information, what is the likely underlying diagnosis responsible for this patient’s symptoms? Comment on the severity of the underlying diagnosis and provide reasons for your answer.
Severe aortic stenosis with impaired LV systolic function. Reasons: Valve area less than 0.7 cm2 and DSI less than 0.2.
Pressure gradients may be low in the presence of LV dysfunction
The aortic valve area places this person into the "critical stenosis" category, unless they are tiny. The critical stenosis threshold is 0.5cm/m2.
The impairment of LV systolic function is evident from the history of SOB, as well as from the Xray findings. This person has heart failure. The man pressure gradient for the LVOT is actually only 18mmHg, which suggests that the poor bewildered ventricle cannot compensate for the narrowed valve, and can no longer generate sufficient pressure to effectively push blood into the systemic circulation. This is what the college means when they say "gradients may be low in the presence of LV dysfunction"; the implication is that the severity of stenosis is underestimated because the LV cannot produce a sufficiently powerful ejection jet for the echosonographer to measure.
This sort of low-gradient aortic stenosis is discussed with due diligence in an article from 2011.
Awtry, Eric, and Ravin Davidoff. "Low-flow/low-gradient aortic stenosis."Circulation 124.23 (2011): e739-e741.