CThSurgery.com
  • HOME
  • CARDIAC SURGERY
    • CORONARY SURGERY
    • VALVE SURGERY
  • THORACIC SURGERY
  • Q BANK
  • AORTIC SURGERY
  • CHEST TRAUMA
  • INSTRUMENTATION
  • RADIOLOGY
    • CARDIAC RADIOLOGY
    • THORACIC RADIOLOGY
    • ABDOMINAL RADIOLOGY
  • PATIENT EDUCATION
  • VIDEO LIBRARY
  • FAMOUS QUOTATIONS
  • RISK ASSESSMENT
    • EUROSCORE II
    • JBS3
    • CHADS2 STROKE IN AF
    • CALCULATE QxMD
  • SITE SEARCH
  • BLOG
  • History of Medicine
  • Cardiac Tumours
  • Hypertrophic Cardiomyopathy
< BACK

Hypertrophic Obstructive Cardiomyopathy (HOCM)


Pathophysiology:
  • Genetically determined primary cardiac muscle disease.
  • 60-70% caused by mutations in sarcomere genes.
  • Characterized by LV Hypertrophy in the absence of other aetiologies.
  • Asymmetric LV hypertrophy especially the interventricular septum is the Hallmark of HOCM
  • There is diastolic dysfunction and varying degrees of dynamic LVOT obstruction.
  • Myocardial ischaemia may also be present.
  • Most commonly results from hypertrophy of the basal septum with mitral-septal contact secondary to SAM of the AML causing (posteriorly directed) MR caused by incomplete leaflet coaptation.
  • Venturi or Drag Effect:
    • High LVOT blood velocities which pull the AML towards the septum (SAM)
      • Causing mechanical impedance to blood flow.
      • Create a pressure gradient between the LV and the aorta at mid-systole.
  • Associated with a variety of anomalies of the mitral valve apparatus:
    • Elongated AML and PML
    • Anterolateral papillary muscle displacement. 
    • Anterolateral papillary muscle insertion into the middle of AML
    • Anomalous chords insertion into the middle of the AML.
  • ​Subsets of HOCM:
    • ​Basal Septal Hypertrophy:
      • ​Associated SAM
      • LVOT Obstruction
    • Pure Mid-ventricular Obstruction:
      • ​Septal contact with papillary muscles causes obstruction to blood flow.
      • MV leaflets do not contribute to the obstruction
      • There is no SAM
      • Causes high intra-ventricular pressure in the apical area and in combination with subendocardial ischaemia, it predisposes to apical aneurysm.
      • Septal Myectomy is performed through an apical incision.
      • this can be combined with subaortic approach to adequately relieve obstruction. 
    • Apical non-obstructive HOCM:
      • ​Non-obstructive and most are asymptomatic.
      • Some may suffer from severe diastolic dysfunction.
      • Severe LV hypertrophy with very small ventricular cavity reducing LV diastolic filling.
      • ​​Apical Myectomy aiming to enlarge the LV volume:
        • Improves haemodynamics
        • Improves functional capacity
        • May delay or eliminate the need for Heart Transplant
Clinical Presentation:
  • Asymptomatic:
    • ​Non-obstructive HOCM.
    • Good Prognosis
    • 10% progress to NYHA class III/IV symptoms.
    • Survival is comparable with age matched controls.
  • Symptomatic Heart Failure caused by diastolic dysfunction, MR and LVOT obstruction.
  • 70% have resting or provoked LVOT obstruction.
  • 25% have resting LVOT gradient >30mmHg.
  • Maximum subaortic pressure gradient >30mmHg
    • Resting or after provocation.
    • Diagnostic
    • Predicts HF and poor prognosis
  • Syncope due to reduced CO from LVOT obstruction.
  • Angina:
    • Coronary microvascular abnormalities.
    • Inadequate capillary densities for the degree of hypertrophy. 
  • Arrhythmias:
    • Supraventricular and ventricular arrhythmias.
    • Sudden cardiac death 0.5 - 1.5% / year
    • more common in patient >30 years old.
    • Rare > 60 years of age.
    • Increased risk when associated with:
      • History of Cardiac arrest.
      • Family history of HOCM-related sudden death.
      • Sustained VT
      • Recurrent prolonged episodes of non-sustained VT. 
      • Massive LVH >30mm
      • Apical LV aneurysm.
      • LGE >15% of LV mass.
      • End-stage HOCM with EF <30% and an Apical LV aneurysm.
    • ​Atrial Fibrillation: 
      • in 20% due to left atrial dilatation.
      • Common in advanced HF and systolic dysfunction.
      • Poorly tolerated due to loss of atrial kick with severe LVH causing reduced CO.
      • A predictor of poor outcome.
      • Treated with:
        • amiodarone.
        • anticoagulation.
        • Catheter AF ablation.
        • Maze procedure at the time of surgical myectomy.
    • Advanced HF with systolic dysfunction that may require Heart Transplant.​​​
Preoperative Evaluation:
  • TTE:
    • Most commonly used imaging to assess:
      • LV morphology including the subaortic area.
      • Haemodynamics by Doppler.
      • identify SAM and associated posteriorly directed MR jet.
      • Intrinsic mitral valve disease or anomalies of the mitral apparatus.
      • Intra-operative TOE to further assess the Mitral Valve.
  • Provocative Tests:
    • For latent LVOT obstruction in patients with exertional symptoms patients with no or minimal LVOT gradients at rest.
    • Valsalva manoeuvres, amyl nitrate inhalation or simple exercise to elicit outflow tract obstruction murmur.
    • Confirmed using these manoeuvres with TTE.
    • Failure to confirm LVOT obstruction will necessitate further tests.
  • Cardiac Catheterisation: 
    • Suspected labile LVOT obstruction not confirmed on TTE.
    • Provocative Tests:
      • Isoproterenol stimulation.
      • Nitrates infusion.
      • Eliciting PVC.
    • Documentation of LVOT gradient >50mmHg confirms the diagnosis.
Management:
  • Consensus guidelines recommend initial medical therapy for Obstructive HOCM with:
    • Beta Blockers.
    • Calcium channel blockers
    • +/- Disopyramide (Class IA anti arrhythmic Na Channel Blocker)
  • Invasive Relief of LVOT obstruction: 
    • those who continue to be symptomatic under optimal therapy:
      • with impaired functional capacity.
      • Subaortic pressure gradient >50mmHg (at rest or after provocation)
    • Do not tolerate side effects of medications.
  • Transaortic septal myectomy is the standard treatment for septal reduction.
    • Survival after myectomy for obstructive HOCM is similar to non-obstructive HOCM
    • Survival after myectomy is superior to unoperated obstructive HOCM.
    • Evidence for beneficial effect on late survival:
      • Reduced incidence of ICD discharges.
      • Diminished MR
      • Improved PHT
      • Degree of reversed myocardial remodelling.
    • It is also possible to perform for other subsets of HOCM.
  • Apical Myectomy:
    • Used for pure midventricular obstruction 
      • To enlarge LV volume and improve LV Filling.
      • Provides immediate relief of symptoms.
      • Has excellent long-term outcome.
      • Eliminate or delays the need for Transplant
    • Can be combined with Subaortic Myectomy to achieve adequate relief of obstruction.
  • Contraindications to Surgical Myectomy:
    • General contraindications for Cardiac Surgery:
      • Advanced Age.
      • Frailty.
      • Multiple Comorbidities that limit expected survival.
    • Alcohol (Ethanol) Septal Ablation: ​​may be an alternative choice for High Risk Patients with contraindications to surgical myectomy.​
Picture
Septal myectomy performed through a low oblique aortotomy extending into the noncoronary sinus using ​no. 10 blade.
(Copyright ©2015, Mayo Foundation)
Picture
Long-segment septal hypertrophy may require both a transaortic approach and a transapical approach. 
(Copyright ©2017, Mayo Foundation)
Alcohol (Ethanol) Septal Ablation:​
  • Also known as:
    • Percutaneous Transluminal Septal Myocardial Ablation
    • Trans-coronary ablation of Septal Hypertrophy.
    • Non-Surgical Septal Reduction Therapy.
  • Relieves obstruction by creating a localized myocardial infarction in the basal septal muscle. 
  • Following remodelling of this area, the LVOT is widened, relieving the obstruction.
  • Improves symptoms and increases exercise capacity.
  • Benefits are comparable in younger and older (age >60 year) patients
  • Procedure:
    • During Cardiac Catherization the First and Second septal perforator branches of the LAD are injected with Ethanol to create a localized controlled MI in the basal septum 
    • Remodelling over time will widen the LVOT and relieves the obstruction.
    • A Large scar is created (10%) of total LV mass.
    • MCE (Myocardial Contrast Echocardiography):
      • Delineate the size of the septal vascular area
      • Predict the infarct size.​
      • May lower the risk of CHB requiring PPM. 
  • Drawbacks:
    • Repeat Ablation may be required in 6%.
    • Conflicting data regarding efficacy in marked septal thickness:
      • Survival is significantly worse in septal thickness >25mm
      • Better long term survival in septal thickness <16mm but with increase early complication.
  • Complications:
    • Coronary artery dissection (LAD 1.8%).
    • Pericardial effusion (0.6%)
    • Large MI secondary to escape of ethanol from the target vessel to another coronary artery (usually the LAD).
    • Complete Heart Block ( requiring PPM 10%) (More RBBB being supplied by the septal perforators)
    • Ventricular Tachyarrhythmia 
    • Arrhythmic Death (VF 2.2%) (there is no definitive evidence that septal ablation increased sudden cardiac death)
    • VSD ( should not be performed with septal thickness <15mm)
Picture
Depiction of alcohol (ethanol) septal ablation
© 2021 UpToDate, Inc. and/or its affiliates. (Graphic 78141 Version 6.0)
Comparison between Surgical Myectomy and Alcohol Ablation:
  • Uncertain effectiveness in massive LV hypertrophy (>30mm), surgical myectomy should be considered instead.
  • Surgical Myectomy results in significantly lower residual LVOT gradients.
  • No significant difference in long-term survival.
Surgical Myectomy
Alcohol Septal Ablation
Higher success rate 90-95%
Success Rate 80-90%
Immediate sustained relief of LVOT obstruction and concomitant MR
Delay up to 3 months in improvement
Ability to obtain tissue biopsy
No Biopsy
Lower incidence of CHB 3%
Incidence of CHB 10%
Better Symptom resolution
Proven long-term efficacy (>20 years)
More chances of success in massive septal hypertrophy (>30mm)
Avoided in massive septal hypertrophy (>30mm)
No damage distal to target area
Risk of myocardial damage distal to the target area
Ability to perform concomitant procedures (AF ablation, CABG, MR repair/replacement)
Avoidance of Sternotomy and CPB especially in high risk patient,  shorter hospital stay, lower costs.
May reduce the risk of Sudden Cardiac Death and ICD discharges
Lower Risk of VSD

HOCM: Hypertrophic Obstructive Cardiomyopathy, ​LV: Left Ventricle, LVOT: Left Ventricular Outflow Tract, CO: Cardiac Output
AML: Anterior Mitral Leaflet, PML: Posterior Mitral Leaflet, MR: Mitral Regurgitation, LGE: Late Gadolinium Enhancement, PHT: Pulmonary hypertension, CHB: Complete Heart Block, ​PPM: Permanent Pacemaker 

Optimized for Google Chrome, Microsoft Edge and Mozilla Firefox
© COPYRIGHT 2021. ALL RIGHTS RESERVED.