Close
Help


Interview with Dr Sandor J. Kovacs

Posted Mon, May, 11,2015

This author interview is by Dr Sandor J. Kovacs, of Washington University School of Medicine. Dr Kovacs' full paper, Diastolic Function in Heart Failure, is available for download in Clinical Medicine Insights: Cardiology.

Please summarise for readers the content of your article.

The focus is on the physiology of diastole in the normal heart, providing a better understanding of what actually happens in low LVEF or normal LVEF heart failure. The rules that govern the physiology are that the four chambered heart is a near perfect constant volume pump and that all hearts initiate filling by being mechanical suction (volume) pumps. What differs between hearts are the chamber properties of stiffness and relaxation modulated by load that determine the Doppler E-wave. The role of stiffness and relaxation can be mathematically quantified by analyzing E-waves via the Parametrized Diastolic Filling formalism. This approach converts quantifying diastolic function based on E-wave analysis from the conventional, visually determined triangle shape approximation that provides Epeak, Eduration, Edeceltime, E VTI etc. to solving the 'inverse problem of diastole' by using the actual, curvilinear E-wave contour as input and determining chamber properties of stiffness and relaxation, modulated by load as output. This method has been extensively validated is a wide range of clinical subsets. Successes of the approach include: solution of the load independent index of diastolic function problem, solution of the isovolumic relaxation problem, recognition that the LV volume at diastasis is the physiologic equilibrium volume, recognition that vortical flow can generate the Doppler L-wave in both the LV and the RV, presence of mitral annular oscillation after E' is normal and its loss indicates relaxation related diastolic dysfunction. The approach also clarifies that torsion is CANNOT be the source of ventricular suction -it is the result of fiber orientation. Suction is due to recoil (titin, extra cellular matrix, visceral pericardium, etc.) in dextrocardia, where torsion is in the opposite direction, you still get suction.

How did you come to be involved in your area of study?

As a board-certified invasive cardiologist with a background in physics and engineering, it is natural to apply the problem solving methods of the physical sciences to the physiology encountered in everyday clinical practice and thereby clarify the mechanism of unexplained observations.

What was previously known about the topic of your article?

Although mathematical modeling of physiology has been performed for decades, its purpose was to model the existing phenomena usually in terms of analog circuit diagrams requiring coupled partial differential equations and dozens of parameters. The output usually consisted of varying some of these parameters numerically and observing model predicted output of pressures, volumes, flow velocities etc. Because of their complexity these models were not invertible -meaning actual pressures, volumes and flows could not be used as input to uniquely generate model parameters. We avoid this problem by using a linear modeling approach where physiologic data can be used as input to generate unique model parameter values. The price we pay, is a lumped parameter approach -which, for diastolic function, combines all aspects of the (complicated 3-D) physiology that generate a restoring force for LV recoil into a linear, bidirectional (1-D) spring. Model predicted E-wave contours and actual E-wave contours show superb agreement validating the method. The overall approach has been also used to solve the isovolumic pressure decay problem. Specifically model predicted, that tau, the time constant of isovolumic relaxation and tauL, the logistic time constant (each of which stem from unrelated approaches) are parametric limits of a single kinematic model of IVR. Many unsolved physiology problems remain that are ideally suited for this type of mathematical modeling.

How has your work in this area advanced understanding of the topic?

Our method, the Parametrized Diastolic filling formalism has been used to characterize diastolic function by a diverse group of investigators domestically and internationally (Belgium, Sweden, Italy, Hungary.)

The recognition that all hearts are suction pumps in diastole is in part due to our efforts as well as solution of the load independent index of diastolic function problem and the recognition of the diastolic volume pumping vs. systolic pressure pumping roles of the heart. In addition our elucidation of near perfect constant-volume pump 4-chamber physiology has stimulated additional work and lead to the recognition of the volume at diastasis as the in vivo equilibrium volume of the LV.

What do you regard as being the most important aspect of the results reported in the article?

Mathematical modeling of the physiology based on motion (kinematic modeling, Newton's Laws) allow DF to be extremely well approximated. It thereby advances state of the art beyond the current determination of DF via E-wave analysis performed 'by eye' and places it on a mechanistic, physiologic causality based foundation. Broad clinical application will require incorporation of the approach on commercially available imaging platforms.

share on

Posted in: Authors

  • Efficient Processing: 4 Weeks Average to First Editorial Decision
  • Fair & Independent Expert Peer Review
  • High Visibility & Extensive Database Coverage
Services for Authors
What Your Colleagues Say About Libertas Academica
testimonial_image
I was delighted to submit an invited review on cluster headache pharmacology.  As someone who writes a few papers per year on these subjects, I appreciated that the submission, review and approval process for the paper was smooth and efficient. Our reviewers raised important points that improved the overall quality of the manuscript. Overall a very positive experience.
Dr Michael J. Marmura (Thomas Jefferson University, Philadelphia, PA, USA)
More Testimonials

Quick Links


New article and journal news notification services
Email Alerts RSS Feeds
Facebook Google+ Twitter
Pinterest Tumblr YouTube