Echo in hypertrophic obstructive cardiomyopathies

hocm

1. Echocardiographic evaluation of Hypertropic obstructive cardiomyopathy Dr.S.R.Sruthi Meenaxshi MBBS, MD, PDF

2. Left ventricular cavity dimensions

3. Hypertrophic cardiomyopathy Hypertrophic cardiomyopathy (HCM) is characterized by increased left ventricular (LV) mass, which is quantitated by determining the wall thicknesses and estimating the LV wall mass. When these findings are present without apparent etiology, the cause of hypertrophy in the majority of cases is mutation in a gene encoding cardiac sarcomeric proteins .

4. The echocardiographic diagnosis of HCM is based upon the finding of an otherwise unexplained hypertrophied, nondilated LV A septal wall thickness ≥15 mm has been commonly used to diagnose HCM (both ACC/AHA and ESC guidelines), although other causes for hypertrophy must be excluded and some patients with HCM do not meet this threshold for septal thickness

5. The degree and distribution of left ventricular hypertrophy (LVH) in HCM are variable, and include septal hypertrophy with or without obstruction to LV outflow, concentric hypertrophy apical hypertrophy hypertrophy of the LV free wall right ventricular hypertrophy

6. One characteristic pattern is asymmetric septal hypertrophy (ASH) with wall thickness greatest at the basal septum. ASH is recognized by a septal to posterior wall ratio of 1.5 to 1. 

7. In a more unusual and often more clinically benign variant of HCM, the apex is the site of the greatest hypertrophy Apical hypertrophy is more difficult to identify by echocardiography because the apical myocardium is more difficult to image 

8. When this condition is suspected ( eg , by finding deeply inverted precordial T waves on ECG), it is helpful to use an echocardiographic contrast agent to confirm the diagnosis and identify the small apical aneurysm that may form distal to the obstruction Cardiac magnetic resonance imaging is a preferred imaging test for identification/exclusion of the apical hypertrophic syndrome since it can detect apical aneurysms missed by echocardiography. 

9. Echocardiographic features    The echocardiogram with Doppler is the most practical means to assess the hemodynamics of HCM. Approximately 20 to 25 percent of patients have a resting left ventricular outflow tract (LVOT) gradient of greater than 30 mmHg However, when the obstruction is dynamic ( ie , provocable but mild or absent at rest), the task of the echocardiographic laboratory is more difficult

10. Asymmetrical septal hypertrophy e point septal contact

11. HOCM

12. DAGGER SHAPED FLOW DISTAL TO HYPERTROPHIED SEPTUM

13. Systolic anterior motion of the mitral leaflet causing left ventricular outflow tract obstruction note the posteriorly directed MR jet

14. M mode through the aortic root at aortic level shows midsystolic flutter or notch- lobster claw abnormality due to impact of dynamic subaortic obstruction on the behaviour of aortic valve

15. Lobster claw abnormality

16. Use of Doppler techniques, particularly continuous wave, is mandatory. This modality is typically used to measure the systolic flow velocity in the LVOT and mid cavity at rest and during maneuvers ( eg , Valsalva; normal 0.9 m/second) Doppler in this setting will also enable the recognition of dynamic mitral regurgitation that often appears with a posteriorly directed jet in concert with outflow tract obstruction.

17. Patients with LVOT obstruction often have the following features: Asymmetric septal hypertrophy Systolic anterior motion of the mitral valve (SAM) Crowding of the mitral apparatus by the LVOT Partial early systolic closure or notching of the aortic valve Calcification of the mitral annulus frequently accompanies HCM, and, in some patients, this finding is the only clue to the potential for dynamic outflow tract obstruction Mitral regurgitation often accompanies obstruction and the mitral regurgitation jet needs to be distinguished from the gradient jet.

18. Significant hypertrop y of the interventricular septum

19. Strain echocardiography    Strain is measured by speckled-tracking measures of both global and regional ventricular function, and can detect reduced myocardial function in HCM It also correlates with myocardial fibrosis and predicts ventricular arrhythmias In addition, mechanical dispersion (defined as the standard deviation of time from the onset of the QRS to peak negative strain) was significantly increased in HCM patients and was both related to amount of fibrosis and was an independent predictor of arrhythmia In athletes, mechanical dispersion of longitudinal strain may be superior to global longitudinal strain (GLS) in identifying HCM

20. Patients with HCM have significantly lower longitudinal systolic strain, systolic strain rate, and early diastolic strain rate as compared with concentric hypertrophy due to systemic hypertension Recognition of HCM may be facilitated by recording of strain data in a polar map, which have different patterns among different types of cardiomyopathy GLS is independently associated with outcomes in HCM patients, with GLS greater than -10 percent associated with higher risk of adverse events 

21. Provocative maneuvers    Whenever obstructive or nonobstructive HCM is suspected but not overt, it is often desirable to perform some sort of intervention or provocation during the echocardiographic examination; the most frequently used maneuver is the Valsalva maneuver and the most common pharmacologic intervention is amyl nitrate inhalation

22. Use of Doppler techniques, particularly continuous wave, is mandatory. This modality is typically used to measure the systolic flow velocity in the LVOT and mid cavity at rest and during maneuvers (normal 0.9 m/second) Doppler in this setting will also enable the recognition of dynamic mitral regurgitation that often appears in concert with outflow tract obstruction.

23. Systolic anterior movement of the mitral valve (SAM) on 2D and M-mode imaging provides independent evidence of dynamic obstruction if there is also contact of the mitral leaflet tip and the septum; the more severe the obstruction, the more prolonged the contact

24. If obstruction worsens with provocation, SAM will also worsen. SAM is graded as follows: ●0 = absent. ●1+ = present, with a minimum distance between the mitral valve and ventricular septum during systole >10 mm. ●2+ = without mitral-septal contact, but with a distance of <10 mm between the mitral valve and septum. ●3+ = brief mitral-septal contact (<30 percent of echocardiographic systole). ●4+ = prolonged apposition of the mitral valve leaflet with the septum (>30 percent of echocardiographic systole). ●Inspection of the aortic valve at the peak of provocation will provide secondary evidence of obstruction by demonstrating early systolic closure (producing notching, also known as a peak and dome configuration on M-mode echocardiography)

25. A Valsalva maneuver is usually performed first, and if it fails to provoke changes, amyl nitrite  inhalation may sometimes be used. During this more vigorous provocation the same structures are monitored. It is ideal during any intervention to have someone performing auscultation. If technical problems interfere with echocardiography or Doppler, detection of a new or worsening murmur, particularly if intense, may be sufficient to identify a culprit condition. Exercise testing may also be used to evaluate this condition. We use supine bicycle so that it is possible to image the heart and sample flow by Doppler during and after the stress test. In this way changes in gradient, severity of mitral regurgitation, and rhythm may be sought. Note that the dynamic outflow gradient often does not worsen until the immediate post-exercise period. This behavior of dynamic obstruction often mimics a common symptom complex in HCM

26. Differential diagnosis    The differential diagnosis of familial HCM includes LVH secondary to other disorders as well as other causes of HCM morphology such as amyloidosis LVH is considered secondary when due to an identifiable disorder such as hypertension or aortic stenosis. As noted above, these disorders are not classified as cardiomyopathies. Secondary LVH is most commonly encountered as a complication of hypertension. The presence of LVH in a hypertensive subject increases the likelihood of cardiovascular morbidity and mortality 

27. Echocardiographic features of secondary left ventricular hypertrophy   Echocardiography is the procedure of choice for identifying secondary LVH since the sensitivity of the various electrocardiographic (ECG) criteria may be as low as 7 to 35 percent with mild LVH and only 10 to 50 percent with moderate to severe disease 

28. The hypertrophy is usually asymmetric in inherited HCM, and symmetric in secondary disease The predictive accuracy of the pattern of hypertrophy for genetically determined versus secondary hypertrophy, however, is low.

29. Sigmoid septum   Focal apparent hypertrophy of the basal interventricular septum (known as sigmoid septum or angulated septum) occurs commonly in older adults, seemingly as the result of an age-related shift in the orientation of the LV long axis from vertical to horizontal. Contrast imaging of the LV suggests that there is little, if any, hypertrophy. As a rule, if the LV wall is not thickened and LV volume is normal, an elevated calculated LV mass in a patient with sigmoid septum is likely artifactual.