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Sometimes Less is More

A 64-year-old male presented to emergency room (ER), with complaints of shortness of breath for one day. He had a past medical history of hypertension, end stage renal disease on hemodialysis (HD), and grade I obesity. He reported that he missed his last HD session, which was two days prior to presentation. He denied any chest pain, palpitations, cough, or fever. Patient further mentioned that he was able to walk >10 blocks without any chest pain or shortness of breath until a couple days ago. In the ER, examining physician documented presence of a systolic ejection murmur heard best at the second right intercostal space and bilateral rales, 1+ pedal edema; jugular venous distention of 4cm. Urgent transthoracic echocardiogram (TTE) was ordered by ER physician to further investigate the aortic stenosis (AS) murmur. TTE showed aortic valve area 0.98cm2, mean gradient 32mmHg, aortic jet velocity 3.5m/s; mild left ventricle (LV) concentric hypertrophy with grade 1 diastolic dysfunction, and LV ejection fraction of 60-65%. Subsequently, patient was admitted to cardiac telemetry and primary team consulted renal and cardiothoracic (CT) team for HD and for aortic valve replacement (AVR), respectively.

CT surgery team requested cardiology consult as a part of pre-operative assessment for possible surgical AVR. Physical examination by the attending cardiologist was remarkable for II/VI mid-systolic peaking crescendo-decrescendo murmur with normal carotid pulse upstrokes. Cardiac catheterization was recommended for further evaluation as there was discrepancy between the findings on noninvasive testing and physical examination regarding severity of the AS. Cardiac catheterization revealed non obstructive coronary artery disease (30% stenosis of mid RCA) and moderate AS (aortic valve area 1.38cm2, mean gradient 28mmHg, aortic jet velocity 3.3m/s). During recovery period patient developed hematoma at access site (right groin), which was managed conservatively but resulted in prolongation of his hospital stay by 48 hours. In the meantime, the patient underwent hemodialysis and had symptomatic relief in his dyspnea. He was discharged home to follow up with his outpatient hemodialysis center.

 

Perspective:

This gentleman presented to ER with complain of shortness of breath after missing a HD session. Although, not incorrect, the systolic murmur heard by ED physician led to a cascade of downstream testing. In fact, the ‘benign’ ‘non-invasive’ testing ordered as a part of comprehensive work-up led to a delay for patient getting the HD session. Physical examination is an essential part of accurate assessment of a patient’s disease process. However, our daily practice has been increasingly occupied by ‘tunneled vision’ of things.

Aortic stenosis (AS) is one of the most common valvular diseases associated with systolic murmur in the elderly population1. An essential part of physical exam of AS is assessing the severity. Munt et al, found significant correlation of physical exam findings like grade of murmur and timing of murmur peak with severity of AS2. Further, delay in carotid upstroke and decreased amplitude was well associated with increasing grade of AS severity as measured by aortic valve area (AVA). Although, one may argue that physical exam is limited by observer expertise and inter-observed variability3, echocardiographic parameters have their own pitfalls. The AVA measurement depends on accurate evaluation of LVOT diameter, which has a variability rate of 5-8% thus providing a significant potential for error4. Further, co-existing LV dysfunction or valvular jets (e.g. MR, AR) can interfere with precise interpretation of echocardiographic parameters.

In summary, the patient should have received urgent HD on presentation. The work up for systolic murmur would have been more appropriate on an outpatient basis. This particular scenario also brings into picture the rising health care costs in the United States, contributed by both additional testing and prolonged hospitalizations. Overall, it is worth concluding that careful physical examination and assessment of the patient is foremost to efficient and ‘do not harm’ philosophy of medicine.

 

References:

1) Osnabrugge R, Mylotte D, Head SJ, Van Mieghem NM, et al. Aortic Stenosis in the Elderly Disease Prevalence and Number of Candidates for Transcatheter Aortic Valve Replacement: A Meta-Analysis and Modeling Study. J Am Coll Cardiol. 2013;62(11):1002-1012.

2) Munt B, Legget ME, Kraft CD, Miyake-Hull CY, et al. Physical examination in valvular aortic stenosis: Correlation with stenosis severity and prediction of clinical outcome. Am Heart J 1999;137:298-306.

3) Stout KK, Otto CM. Quantification of Valvular Aortic Stenosis. ACC current journal review Mar/Apr 2003.

4) Baumgartner H, Hung J, Bermejo J, Chambers JB, et al. Echocardiographic assessment of valve stenosis: EAE/ASE recommendations for clinical practice.

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Atrial Structure and Function – Methodology of Atrial Strain

“If echocardiographers are to stand still, depend on standard 2D echo imaging using equipment produced a decade ago and not upgraded since, perform “ejectionfractionograms,” focus primarily on the left ventricle and simply ‘‘eyeball’’ the other chambers, and avoid new methods such as strain imaging and contrast echo because they are perceived as ‘‘a waste of time’’, then I fear that echocardiography will be passed by. As the dinosaurs illustrated, we need to adapt and continue to evolve, or face the consequences.”   –Alan Pearlman- JASE editor, 2010

My research experience focused on heart failure and atrial function. I conducted medical research on the derivation and validation of novel echocardiographic approaches to myocardial and atrial deformations. I have been heavily involved with all projects using strain echocardiography at Duke University (approximately 50 projects over the last 7 years). I have completed over 10,000 speckle tracking strain measurements analysis on different cardiac diseases and on different cardiac chambers.

Both left and right atrium function moderate ventricular function through three components:

  1. Atrial diastole (Reservoir phase) or expansion during ventricular systole. This function is dependent on ventricle longitudinal function, atrial wall elastance and venous return. Reservoir function may increase during physical activity in a normal healthy heart. Increase of this phase help to increase ventricular filling.
  2. Passive atrial systolic phase (Conduit function) during ventricle early diastole. This phase is dependent on the ventricle end-diastolic pressure. Conduit function does not affect by physical activity.
  3. Active atrial systolic phase (Active contraction) (when sinus rhythm is present) during ventricle late diastole. This phase is dependent on atrial wall contractile properties and ventricular end diastolic pressure. Active contraction function is affected by physical activity in a normal heart.

Traditionally atrial function was measured indirectly by using volumes. However, this is still not resembling the actual atrial deformation and mechanics. With a high feasibility and reproducibility of speckle tracking strain echocardiography, atrial function is ready to be a part of an echo report in a daily clinical practice.

Speckle tracking strain imaging has been around for quite a while and we celebrated the first decade 3 years ago, whereas the technique described in 2004 (Leitman M-JASE) and clinical applications appeared around 2005 (Notomi Y- JACC). Since then, the interest has risen dramatically and so far, we have > 5000 publications on this topic. Left ventricular (LV) ejection fraction (LVEF), the most widely used measure of cardiac function, has important limitations including low sensitivity for incident HF, technique-related variability and does not directly assess LV contractility. Global longitudinal strain (GLS) is the most studied among strain parameters and its prognostic value has been demonstrated in several clinical scenarios.

GLS inter-Vendor variety has dramatically dropped over a short period of time. However, still if we look at the same images with different software vendors, we may have different values. This difference is due to several factors: 1) Image quality and acquisition; 2) Software used; 3) Where to measure (endocardial, myocardial, median); 4) Post-processing of data; 5) Patients age, gender variabilities and loading conditions. With regard to regional (segmental) function, we now have, for the first time, the possibility to measure regional myocardial function. However, I think this is more challenging than GLS, and there is still progress to be made. The challenges become because we have only one segment to work with, and less data to average. Tracking quality becomes more important, regional artifacts matters more, definition of sample position more relevant, and more importantly, we cannot simply measure peak values anymore. For regional analysis, the strain curve shape (not peak values, because peak values can be the same), become critical.

atrial function and structure

Technical factors that may influence atrial strain values:

  • Optimization of images quality and frame rates are vital (ideally, no less than 40 fps).
  • Start tracing at the lateral valve annulus, along the endocardial border of the atrial lateral wall, atrial roof, atrial septal wall, and ending at the septal valve annulus.
  • Difficulties tracking atrial segments relate to the thin wall, insertion of blood vessels and atrial appendages.
  • Significant age-related reductions in strain have been reported. Similarly, sex-related differences have been described, with lower deformation noted in male patients than in female patients.
  • Atrial strain increases in response to early physiological heart rate increase in the setting of exercise in normal patients. However, decreased values are found in the setting of pathological heart rate increase.
  • Atrial strain also affected by loading condition. Reporting, BP, HR and heart rhythm, IVC diameter are crucial.
  • Atrial phases function (Reservoir, conduit and atrial) is also dependent on the ventricular function. Report both atrial and ventricular functions are important.
  • Atrial strain maybe useful as an early marker of DD.

In summary, I think GLS is ready for clinical practice. Its robust, reproducible and has been shown to add unique data that can guide diagnosis and management. I recommend GLS as a valuable complement to traditional function parameters. Further studies are needed to standardize vendors, recognizing specific strain patterns and to determine if there are age, gender variabilities or loading conditions difference.

 

References:

Myocardial Strain Measured by Speckle-Tracking Echocardiography: Patrick Collier, MD, PHD, Dermot Phelan, MD, PHD, Allan Klein, MD VOL. 69, NO. 8, 2017 – ISSN 0735-1097