HIGHLIGHTS FROM THE INTERNATIONAL HCM SUMMIT VI, PART II

**Because so much HCM information was presented at the Summit, this is the second of multiple blog entries.  Stay tuned to HCMBeat for more highlights from the HCM Summit.  To see Part I of this series of highlights from the HCM Summit VI, click here.**

The 6th International HCM Summit was held October 27, 28 and 29th in Boston, Massachusetts.  This symposium brings together HCM professionals from around the world who are there to learn about and discuss the latest developments in the treatment of HCM.

The symposium was organized by long time HCM expert Dr. Barry Maron and his son, Dr. Martin Maron.  Both Marons are now affiliated with Tufts Medical Center’s Hypertrophic Cardiomyopathy Center.

What follows are summaries from selected talks presented at the meeting.  The presenter and their hospital affiliation are noted below, along with the topic of their presentation.  When possible, you may access the presenters’ slides via hyperlink by clicking on the name. (Note that not all presenters made their slides available).

Dr. Harry Rakowski – Toronto General Medical Hospital, Toronto, Canada -The Role of Echocardiography in the Era of Cardiac MRI

  • In HCM, Echocardiograms are used to continually assess and reassess hypertrophy, obstruction of left ventricular outflow tract and the function of the left ventricle.
  • Echocardiograms assess left atrial function and diastolic dysfunction as well as left ventricular outflow tract gradients:  70% of HCM patients have some form of obstruction:  30% have resting obstruction and 40% have latent obstruction.
  • Exercise stress echocardiography is used to evaluate left ventricular outflow tract gradient in HCM, as well as the degree of mitral regurgitation and blood pressure response to exercise, as well as general evaluation of HCM symptoms on a continuing basis.
  • Echocardiography is important in planning and assessing suitability of invasive procedures such as alcohol septal ablation or myectomy.  They are also important in evaluating the effectiveness of procedures both immediately and in long term follow up.

Debate Between American and European Guidelines in Risk Stratification for Identification of High Risk Patients in Need of ICDs: 

For the European Society of Cardiology (ESC) Guidelines – Dr. Albert Hagege – George Pompidou European Hospital, Paris, France. 

  • Current U.S. guidelines lead to ICD implantation in many people who will never experience sudden cardiac arrest.
  • The number of unnecessary ICD implantations in patients with a single risk factor was significantly reduced by using the ESC score to determine who is a candidate.  This method of risk stratification has been validated by several studies.
  • The ESC online risk calculator can be found online here.

For the American College of Cardiology/American Heart Association Guidelines – Dr. Steve Ommen – Mayo Clinic, Rochester, MN

  • ICDs are recommended for patients who have had a prior sudden cardiac arrest or who have experienced sustained ventricular tachycardia.
  • Recommendations for patients with 1 or 2 risk factors should be individualized based on clinical judgment.  Process should involve shared decision making between patient and physician, including discussion of the need for the device and a thorough discussion of risk and benefits.

Dr. Barry Maron – Tufts Medical Center, Boston, MA – The Implantable Defibrillator: Prevention of Sudden Death

  • ICDs protect patients from sudden cardiac death by terminating potentially lethal ventricular arrhythmias at the rate of 4% for those who have never had a cardiac arrest, and 11% for those who have had a previous arrest.
  • The decision to implant a device must be weighed against the risk of device related complications, which is 5% per year.
  • Through the use of ICDs, mortality rates from HCM are less than or equal to 1% per year.  But, it is difficult to determine who should be implanted with a device.
  • Current risk factors for primary prevention of sudden cardiac arrest as set forth in the ACC/AHA Guidelines include:
    • Family history of sudden death from HCM;
    • Unexplained syncope (fainting);
    • Multiple repetitive non-sustained ventricular tachycardia seen on holter monitor;
    • Abnormal blood pressure response to exercise;
    • Late gadolinium enhancement greater than or equal to 15% of left ventricular mass;
    • Massive left ventricular hypertrophy greater than or equal to 30 mm; and
    • Left ventricular apical aneurysm
  • HCM is very unpredictable.  ICDs may be called on to deliver their first shock many years after implantation.
  • The decision whether to implant a device involves weighing the risk of sudden death against the risk of inappropriate shocks, device recalls, device infection, thrombosis and a potential lead complication rate of 5%/year.
  • The ICD has reduced the annual death rates from HCM over the last 40 years from 4% – 6% in 1975 to 0.5% in 2017.

Dr. Mark Estes, Tufts Medical Center, Boston, MA – Subcutaneous ICDs (S-ICD) and Transvenous ICDs

  • The S-ICD is a departure from the older type of transvenous ICDs because it positions its single lead in the subcutaneous layer of the thoracic cage, thereby avoiding potential complications from the wear of traditional transvenous leads.
  • Best candidates for the S-ICD are patients with genetic conditions that are high risk for sudden death like HCM, Long QT Syndrome and Brugada Syndrome.
  •  It is also indicated for those patients who are at high risk for lead complications, such as those patients who:
    • are at high risk for lead complications;
    • are young and active;
    •  have had previous device infections;
    • are diabetic or immunocompromised
    • where there is no access to veins or they are occluded or undesirable
    • where there is history of previous infection
  • HCM patients may require higher defibrillation thresholds than those with other cardiomyopathies.  Also, there is potential for inappropriate shocks due to oversensing.  Hence, the utility of the S-ICD in the HCM population is currently being followed in multiple registries.
         Advantages of S- ICD
  • No transvenous lead complications

         Disadvantages of S-ICD

  • Not able to act as pacemaker
  • Remote monitoring is not available.
  • Larger generator unit implanted on side of patient.  More obtrusive.
  • Late gadolinium enhancement (LGE), which is present in approximately 60% of HCM patients, indicates myocardial fibrosis in HCM.
  • The mere presence or location of LGE is not meaningful in HCM, but the extent of fibrosis identified by LGE, if more than 15%, can provide an additional risk factor for sudden cardiac arrest or may indication progression toward end stage disease.
  • Cardiac MRI should be considered as part of the initial HCM evaluation in most HCM patients.

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