Septal Knuckle Hypertrophy Causing Lvot Obstruction

no clear etiological relationship to hypertrophic cardiomyopathy. Nevertheless, the prominent septal "knuckle" found in DUST may cause dynamic outflow tract obstruction (Fig. 24).

Mitral Regurgitation in Hypertrophic Cardiomyopathy

A posteriorly directed jet of mitral regurgitation typically accompanies SAM of the mitral valve for reasons explained previously (Figs. 18 and 19). It temporally follows the onset of LVOT obstruction and care should be taken not to confuse its Doppler velocity profile with that of LVOT obstruction. The peak gradients, timing, and configuration of the spectral Doppler profile help to differentiate between the two.

Diastolic Dysfunction in Hypertrophic Cardiomyopathy

Diastolic filling of the left ventricle is impaired in about 80% of individuals with hypertrophic car-diomyopathy, and can even be observed in asymptomatic patients without overt hypertrophy but who are genetically affected. No clear relationship exists between the severity of hypertrophy and the severity of diastolic dysfunction. Asynchronous myocardial relaxation of the hypertrophied muscle can lead to complex patterns of intracavitary flow during diastole.

Echocardiography in Septal Ablation and Myectomy-Myotomy

Echocardiography plays a central role in identifying clinically significant LVOT obstruction that requires intervention, i.e., septal ablation or myectomy-myotomy of the hypertrophied muscle. Intra-procedural echocardiography with myocardial contrast imaging has become routine during alcohol septal ablation (Fig. 25).

The septal perforating branch of the left anterior descending coronary artery that supplies the hyper-trophied septum (where it contacts the anterior mitral leaflet) is cannulated via a percutaneous transluminal approach and myocardial contrast agent then injected. Intraprocedural echocardiography is essential to guide and monitor the procedure and dehydrated alcohol is

Systolic Anterior Motion Mitral Valve

Fig. 19. Systolic anterior motion of the mitral valve (SAM). SAM of the mitral valve dynamically obstructs normal left ventricular outflow (LVOT). Note the anterior movement of both mitral leaflets (and supporting mitral structures) and the incomplete coaptation at a point halfway the body of the elongated mitral leaflets. These result in the characteristic posteriorly directed jet of mitral regurgitation (Fig. 18). (Please see companion DVD for corresponding video.)

Fig. 19. Systolic anterior motion of the mitral valve (SAM). SAM of the mitral valve dynamically obstructs normal left ventricular outflow (LVOT). Note the anterior movement of both mitral leaflets (and supporting mitral structures) and the incomplete coaptation at a point halfway the body of the elongated mitral leaflets. These result in the characteristic posteriorly directed jet of mitral regurgitation (Fig. 18). (Please see companion DVD for corresponding video.)

Table 11 Systolic Anterior Motion

Hypertrophic cardiomyopathy

Left ventricular hypertrophy

Infiltrative cardiomyopathies with septal involvement

Hypercontractile states

Mechanical causes

Others

Systolic Anterior Motion With Mode

Fig. 20. Systolic anterior motion of the mitral valve (SAM). M-mode at the mitral valve level can reveal the timing and duration of the SAM of the mitral valve leaflets. A linear relationship exists between the time of onset and duration of SAM, and the severity of the dynamic left ventricular outflow tract (LVOT) obstruction (Pollick C. Circ 1984:69, 47). Note that systolic anterior displacement involves not just the anterior mitral leaflet, but also the chordae and papillary muscles—giving appearance of "crowding" during systole on M-mode (arrow labeled SAM).

Fig. 20. Systolic anterior motion of the mitral valve (SAM). M-mode at the mitral valve level can reveal the timing and duration of the SAM of the mitral valve leaflets. A linear relationship exists between the time of onset and duration of SAM, and the severity of the dynamic left ventricular outflow tract (LVOT) obstruction (Pollick C. Circ 1984:69, 47). Note that systolic anterior displacement involves not just the anterior mitral leaflet, but also the chordae and papillary muscles—giving appearance of "crowding" during systole on M-mode (arrow labeled SAM).

injected when the site of maximal obstruction is identified. Improved success rates and fewer complications occur when myocardial contrast echocardiography is employed.

Intra-operative transeophageal echocardiography is routinely employed during surgical myectomy-myotomy of the hypertrophied septum.

Apical Variant of Hypertrophic Cardiomyopathy

A peculiar variant of hypertrophic cardiomyopathy that accounts for near 25% of cases in Japan and 40% in parts of China (but <5% of cases in the United States) is characterized by "giant" negative T-waves on ECG (Fig. 26) and "spade-like" geometry of the left ventricular cavity at end-diastole on 2D echocardio-graphy. It runs a more benign course and presents later than other variants, but unfamiliarity with its ECG findings and echocardiographic features, including complex mitral filling patterns (Figs. 27 and 28) can lead to injudicious management.

Notch Mitral Valve Mode

Fig. 21. Midsystolic aortic valve notch/flutter. M-mode through the aortic root at the aortic valve level. In this elderly woman, a septal "knuckle" shows the impact of dynamic left ventricular outflow tract obstruction on aortic valve behavior. Midsystolic notching and fluttering are common—a reflection of turbulence and dynamic nature of the obstruction—the so-called "lobster claw" abnormality.

Fig. 21. Midsystolic aortic valve notch/flutter. M-mode through the aortic root at the aortic valve level. In this elderly woman, a septal "knuckle" shows the impact of dynamic left ventricular outflow tract obstruction on aortic valve behavior. Midsystolic notching and fluttering are common—a reflection of turbulence and dynamic nature of the obstruction—the so-called "lobster claw" abnormality.

Table 12

Physiological States, Maneuvers, and Interventions That Influence LVOT Gradient in Hypertrophic Cardiomyopathy

Preload

Afterload

Contractility

Valsalva (strain phase) decrease decrease -

Standing decrease - -

Leg raising decrease - -

Exercise increase increase increase

Isometric handgrip - increase -

Tachycardia decrease - increase

Hypovolemia decrease decrease increase

Amyl nitrite inhalation decrease decrease increase

IVCS; general anaesthesia - or decrease - decrease Conditions that decrease preload, lower afterload, and increase contractility generally increase LVOT gradient (and the systolic murmur)

Table modified from Wynne J, Braunwald E. The Cardiomyopathies. In: Braunwald's heart disease—a Textbook of Cardiovascular Medicine, Zipes DP, Libby P, Bonow RO, Braunwald E eds., Elsevier Saunders. Philadelphia, 2005.

IVCS, intravenous conscious sedation; LVOT, left ventricular outflow tract.

Athelete's Heart or Hypertrophic Cardiomyopathy?

Sudden cardiac death in the young, specifically in the athletic population, poses clinical, echocardiography

(and medico-legal) challenges. Hypertrophic cardiomy-opathy is the most common cause of death in athletes. Current data indicate that hypertrophic cardiomyopathy is responsible for up to one-third of such deaths.

Valsalva Lvot

Fig. 22. Valsalva maneuver and hypertrophic cardiomyopathy. Gradients across the left ventricular outflow tract obstruction are influenced by conditions affecting preload (Table 11). A,B show velocities at rest on pulse Doppler with accelerated flow evident on color flow Doppler. In this patient, peak gradients averaged 50 mmHg, but exceeded 100 mmHg during the strain phase of the Valsalva maneuver. This was associated with chest pain he was referred for septal ablation.

Fig. 22. Valsalva maneuver and hypertrophic cardiomyopathy. Gradients across the left ventricular outflow tract obstruction are influenced by conditions affecting preload (Table 11). A,B show velocities at rest on pulse Doppler with accelerated flow evident on color flow Doppler. In this patient, peak gradients averaged 50 mmHg, but exceeded 100 mmHg during the strain phase of the Valsalva maneuver. This was associated with chest pain he was referred for septal ablation.

Late Systolic Peaking
Fig. 23. (Continued)
Dynamic Lvot Obstruction And Hypovolemia

Fig. 23. (A) Exercise stress testing in hypertrophic cardiomyopathy. Stress testing in hypertrophic cardiomyopathy can provide information on gradients that correlate with patient symptoms and serve as a guide to the timing and efficacy of interventions. Systolic frames postexercise show marked ventricular outflow obstruction (top panels) Baseline pulse Doppler (PW) shows shows normal aortic outflow velocities (bottom left panel), which markedly accelerate, exceeding 5 m/s (bottom right panel). (B) Dynamic midcavity obstruction. Sketch depicting late-peaking Doppler velocity envelope in midcavity obstruction in hypertrophic cardiomyopathy involving primarily the midleft ventricular segments and papillary muscles (see also Fig. 27A).

Fig. 23. (A) Exercise stress testing in hypertrophic cardiomyopathy. Stress testing in hypertrophic cardiomyopathy can provide information on gradients that correlate with patient symptoms and serve as a guide to the timing and efficacy of interventions. Systolic frames postexercise show marked ventricular outflow obstruction (top panels) Baseline pulse Doppler (PW) shows shows normal aortic outflow velocities (bottom left panel), which markedly accelerate, exceeding 5 m/s (bottom right panel). (B) Dynamic midcavity obstruction. Sketch depicting late-peaking Doppler velocity envelope in midcavity obstruction in hypertrophic cardiomyopathy involving primarily the midleft ventricular segments and papillary muscles (see also Fig. 27A).

Septal Knuckle

Fig. 24. DUST: discrete/disproportionate upper septal hypertrophy in the elderly. Disproportionate upper septal hypertrophy is commonly seen in othewise normal elderly individuals. Note the relationship of the septal "knuckle" to the left ventricular outflow tract (A) with flow acceleration on color flow Doppler (B). Spectral Doppler envelope shows late-peaking velocities (C). The impaired relaxation pattern (E:a ratio < 1) occurs in normal aging (D).

Fig. 24. DUST: discrete/disproportionate upper septal hypertrophy in the elderly. Disproportionate upper septal hypertrophy is commonly seen in othewise normal elderly individuals. Note the relationship of the septal "knuckle" to the left ventricular outflow tract (A) with flow acceleration on color flow Doppler (B). Spectral Doppler envelope shows late-peaking velocities (C). The impaired relaxation pattern (E:a ratio < 1) occurs in normal aging (D).

Septal Knuckle

Fig. 25. Septal ablation: intraprocedural echocardiography. Images from the same patient in Fig. 23 are obtained pre- and postseptal ablation. At baseline (A) in the cardiac catheterization suite, resting gradient was 50 mm (B) increasing to 100 mmHg with Valsalva (C). Cannulation of the septal artery supplying the offending septal region followed by slow infusion of dehydrated alcohol to ablate the same. Echocardiographic staining of the injected septal region is evident (D). Immediately postprocedure, the resting gradient fell remarkably at baseline (E) and during Valsalva (E). Repeat echocardiography done 2 wk later showed continued echocardiographic and clinical improvement.

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Responses

  • hugo harikkala
    What is a septal knuckle?
    7 years ago
  • aulis
    What is septal knuckle heart?
    6 years ago
  • irene
    Does an LVOT obstruction cause an increase in aortic valve velocity echocardiography?
    4 years ago
  • CAROLA
    What is prominent septal knuckle?
    3 years ago
  • Kibra
    What is discrete upper septal thickening?
    12 months ago
  • laura
    What is a focal knuckle located in the heart?
    1 month ago

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