The American Society of Echocardiography’s 26th Annual Scientific Sessions took place June 12-16 at the Hynes Convention Center in beautiful Boston, MA. Over 5 days, attendees had opportunities to attend hands on sessions, lectures, case-based presentations, and oral and poster research sessions. All abstracts are published in the current issue of JASE and accessible online.
Handheld Ultrasound – Hocus “POCUS”?
Point of care ultrasound (POCUS) was the topic of numerous abstracts and a full Friday afternoon session. Handheld ultrasound devices, such as the popular GE V-scan, are being used by everyone from medical students and ER physicians to seasoned cardiologists. Issues surrounding remuneration, documentation, and education regarding competency have been ongoing issues.
The usefulness of handheld ultrasound was demonstrated in a Young Investigator Award finalist abstract by Bhavnani et al. (abstract YIA-3). During a recent ASE Foundation humanitarian mission to India, 133 people at risk for rheumatic heart disease were assessed using handheld ultrasound. Severe rheumatic valvular disease requiring intervention was identified in 45 participants, who subsequently saw a shorter time to intervention compared to study participants undergoing standard care.
Valvular Heart Disease – Applying Echo Criteria based on the 2014 ACC Valvular Guidelines
The new ACC 2014 valve guidelines (Nishimura et al. Circulation. 2014; 129: 2440-2492) were discussed at several sessions and represent a shift in the staging of valvular heart disease using a 4 stage model similar to that commonly used in heart failure.
Mitral Regurgitation (MR) quantification is evolving, and remains challenging. The newer guidelines have differentiated MR into primary vs. secondary etiologies. Primary MR usually refers to mitral valve prolapse (MVP), although by definition is a pathology related to any component of the valve including leaflets, chordae, annulus or papillary muscles. In secondary MR, the valve is morphologically normal, but prone to geometrical distortions due to LV dysfunction. Effective Regurgitant Orifice (ERO) criteria have changed for grading severe MR, using ≥ 0.20 cm2 for secondary and ≥ 0.40 cm2 for primary MR. This is based on the rationale that secondary MR will have a cresenteric proximal flow convergence leading to subsequent underestimation of ERO using PISA methods. The challenges in this classification were discussed, and an expert panel emphasized that grading of MR should not be based on any sole parameter, but rather the careful consideration of all parameters. Mitral valve surgery is a class I indication in asymptomatic patients if the EF ≤ 60% or if the LVESD ≥ 40 mm.
Rheumatic mitral stenosis has now been re-classified into very severe (MVA ≤1.0 cm2, PHT ≥ 220 ms) and severe MS (MVA ≤ 1.5 cm, PHT ≥ 150 ms).
Aortic Stenosis (AS) has included the identification of “very severe AS” with a peak aortic velocity (V2) of ≥ 5 m/s, given its poor prognosis in population studies with a class IIa recommendation for AVR in asymptomatic patients meeting this criteria. An EF <50% serves as a class I indication for surgery in asymptomatic patients. The definition of severe AS remains unchanged (V2 ≥ 4 m/s, mean gradient ≥ 40 mm Hg) from previous guidelines. Dobutamine stress echocardiography is suggested for patients with an EF <50% to identify low flow/low gradient AS for possible surgery with a definition of test positivity including a V2 ≥ 4 m/s (or mean gradient ≥ 40 mm Hg) and AVA ≤ 1.0 cm2 at any dobutamine dose.
Aortic Regurgitation (AR) markers of ventricular decompensation/dilatation requiring surgery have been lessened with an ESD of ≥ 50 mm (Class IIa) and an EDD of ≥ 65 mm (Class IIb) considered as surgical indications for asymptomatic patients. An EF of ≤ 50% remains a surgical indication as before (Class I). Several panelists at ASE cautioned against the use of single, linear measurements in deciding on suitability for surgery as they will vary based on age and body surface area (BSA). Aortic root measurements remain highly dependent on indexing to BSA, with the newer aorta imaging guidelines also discussed at the meeting.
When size matters – the ASE Chamber Enlargement Guidelines 2015
The biggest change addressed was the definition of LA enlargement. Left atrial volume (measured by area length ellipsoid or disk summation methods) has now been defined by a larger volume based on newer studies. The upper limit of normal has increased to 34 mL/m2 from the previous 2005 document that used 28 mL/m2. An abstract from Montreal by Rebaine et al. (abstract P2-22) found that based on current guidelines, volumetric assessment downgrading would occur in 83% of patients previously classified based on 2005 criteria.
Similarly, the previous guideline from 2005 defined a normal EF as >55% for men and women. The current guideline defines ≥ 52% as normal for males and ≥ 54% for females.
Strain-ing Away to the Future
Speckle tracking derived measures of myocardial mechanics include LV torsion and longitudinal strain. Strain describes the amount of myocardial deformation that occurs regionally or globally. Global longitudinal strain (GLS) has evolved from an esoteric research tool to a commonly used echo modality with many applications. Challenges in measuring strain with different vendor machines and software were discussed.
Strain is a key player in the detection of cancer chemotherapy related cardiotoxicity with agents such as trastuzumab. Several abstracts and sessions drew upon the current ASE expert consensus paper on multimodality imaging following cancer therapy (Plana et al. JASE 2014;27:911-39). Chemotherapy related cardiotoxicity is defined as a drop in EF of 10 points to less than 53%, or is strongly suggested by a relative drop in baseline global longitudinal strain of >15%. An abstract by Olga et al. suggested several echo parameters, including GLS and 3D derived EF, were sensitive in the detection of cardiotoxicity compared to MRI derived makers (abstract P2-26). Another abstract by Fei et al. found that smaller decrements in GLS post chemotherapy for breast cancer were most predictive of subsequent improvements in EF (abstract P1-57).
Strain is a useful tool in the detection of subclinical disease, and in the delineation of regional abnormalities in certain cardiomyopathies such as amyloidosis or HCM. The evolution of strain on population outcomes was perhaps one of biggest shifts in research noted at the meeting.
Several abstracts showed newer insights in the use of GLS:
– GLS was predictive of outcomes post AMI in 638 Korean patients with reduced strain predictive of death (abstract P1-119)
– GLS did not predict the development of LV dysfunction or outcomes following MVR in a Mayo Clinic study (abstract P2-33)
– GLS and apical strain improved in patients following TAVR (abstract P2-55)
Echocardiography and Interventions
Several sessions focused on the integral role echocardiography plays in current transcatheter interventions including MitraClip procedures and TAVR.
The MitraClip is a cobalt chromium clip intervention based on the surgical Alfieri stitch in the treatment of chronic primary MR. Itabashi et al. (abstract P2-43) reviewed mitral valve orifice area (MVOA) by 3D planimetry on 107 patients undergoing MitraClip procedures. They found that a 3D MVOA < 3.9 cm2 was most predictive of a high post-procedure transmitral pressure gradient.
Echocardiography is often present in most cardiac catherization labs peri-procedurally, leading to the development of fused fluoroscopic/echocardiographic imaging (FFEI) that combines and co-registers the echo probe on X-ray imaging. FFEI has been used in adult patients at several centers for MitraClip and TAVR procedures. Jone et al. (abstract P2-157) presented a series of 25 pediatric patients undergoing interventions including shunt closures, percutaneous valve placements, and Fontan fenestration repairs. Using a subjective scale, 80% of these procedures were felt to be “superiorly” performed using FFEI, suggesting it has an important role in pediatric congenital interventions.
A Novel and Therapeutic use for Contrast
Myocardial contrast using microbubbles has been well established for use in left ventricular opacification (LVO) enhancing endocardial definition, and increasing the sensitivity in the detection of LV thrombus.
Young Investigator Award finalist Bruno Tavares (abstract YIA-1) and his colleagues looked at the concept of “sonothrombolysis” in the treatment of STEMI patients. Twenty-four patients presenting with STEMI were randomized to a strategy in which they received high mechanical index impulses using a standard TEE probe during a continuous infusion of Definity microbubble contrast prior to standard PCI. Sonothrombolysis via one of two techniques was associated with higher recanalization rates on angiography and improved cardiac function. There were no observed deaths, and door to needle times were not affected.
The Final Word
Overall the meeting was deemed a success with the largest number of delegates to dates. The abstract committee reviewed a record number of over 700 submissions for consideration. There was truly something for everyone, from sonographers, to general cardiologists, to those involved in echo research. The CSE was well represented with several members providing presentations and CSE president Chi-Ming Chow anchoring a winning effort in a Jeopardy-style echo competition called “Three of a Kind”. There were sessions that ranged from the history of echo to those that showcased innovations within the field.
Dr Sabe De MD FRCPC FASE,
Assistant Professor Dalhousie University
Cardiologist, Cape Breton Regional Hospital