Vinay Pai Ph.D.
Department of Radiology (RESEARCH)
Research Summary
Clinical Motivation:
Chronic heart failure (CHF) patients frequently develop intraventricular conduction delay (e.g. a left bundle branch block (LBBB) pattern), as commonly evidenced by a wide QRS complex; the altered electrical activation sequence can lead to dyssynchronous ventricular activation, ventricular dysfunction, worsening failure and hemodynamic instability. Abnormal activation decreases the work efficiency of the heart by decreasing stroke volume and contractility, and increasing end-diastolic volume due to dyssynchronous shortening and delayed relaxation. Cardiac resynchronization therapy (CRT) is a recently developed approach for treating these conduction abnormalities by using left ventricular (LV) or biventricular pacing to alter the sequence of electrical activation in the heart. However, the relation between the electrical dyssynchrony and the mechanical dyssynchrony is still not very well understood. This is one reason why CRT has 20 - 30% nonresponders to its use. Understanding and quantifying mechanical dyssynchrony can provide a potentially valuable means for determining the patient population which can best use CRT. This may also be useful in optimizing the positioning of electrical leads in resynchronization therapy.
Potential Solution:
MRI tagging permits noninvasive quantification of LV function, making it feasible to measure the spatial and temporal distribution of mechanical activation. Our current work has focused on developing very high temporal and spatial resolution MRI tagging schemes in order to track mechanical dyssynchrony. This should allow us to compute local strains over the entire right and left ventricle of the heart. This approach is currently implemented with a high spatial (800 micron in direction normal to tags) and high temporal resolution (7 ms) scheme, which acquires 2D slice cine data in 4 minutes of free breathing. The work is now progressing towards acquiring very high resolution (1.5 ? 2 ms) data in a breathhold by utilizing novel imaging approaches, in conjunction with parallel MR imaging. This technique is also being utilized to acquire high resolution volume tagged MRI data under free-breathing conditions.
Other Applications / Motivations:
High temporal resolution imaging is also being developed as a tool to study valvular dynamics. The primary focus is to study native valves and examine the feasibility of using high temporal MRI to understand the mechanisms of valve failure. Another focus area is to study Tetralogy of Fallot patients post-repair to determine indicators for reoperation.
Chronic heart failure (CHF) patients frequently develop intraventricular conduction delay (e.g. a left bundle branch block (LBBB) pattern), as commonly evidenced by a wide QRS complex; the altered electrical activation sequence can lead to dyssynchronous ventricular activation, ventricular dysfunction, worsening failure and hemodynamic instability. Abnormal activation decreases the work efficiency of the heart by decreasing stroke volume and contractility, and increasing end-diastolic volume due to dyssynchronous shortening and delayed relaxation. Cardiac resynchronization therapy (CRT) is a recently developed approach for treating these conduction abnormalities by using left ventricular (LV) or biventricular pacing to alter the sequence of electrical activation in the heart. However, the relation between the electrical dyssynchrony and the mechanical dyssynchrony is still not very well understood. This is one reason why CRT has 20 - 30% nonresponders to its use. Understanding and quantifying mechanical dyssynchrony can provide a potentially valuable means for determining the patient population which can best use CRT. This may also be useful in optimizing the positioning of electrical leads in resynchronization therapy.
Potential Solution:
MRI tagging permits noninvasive quantification of LV function, making it feasible to measure the spatial and temporal distribution of mechanical activation. Our current work has focused on developing very high temporal and spatial resolution MRI tagging schemes in order to track mechanical dyssynchrony. This should allow us to compute local strains over the entire right and left ventricle of the heart. This approach is currently implemented with a high spatial (800 micron in direction normal to tags) and high temporal resolution (7 ms) scheme, which acquires 2D slice cine data in 4 minutes of free breathing. The work is now progressing towards acquiring very high resolution (1.5 ? 2 ms) data in a breathhold by utilizing novel imaging approaches, in conjunction with parallel MR imaging. This technique is also being utilized to acquire high resolution volume tagged MRI data under free-breathing conditions.
Other Applications / Motivations:
High temporal resolution imaging is also being developed as a tool to study valvular dynamics. The primary focus is to study native valves and examine the feasibility of using high temporal MRI to understand the mechanisms of valve failure. Another focus area is to study Tetralogy of Fallot patients post-repair to determine indicators for reoperation.
Research Information
Research Interests
Studying cardiac mechanics utilizing magnetic resonance imaging. Nonbreathhold threedimensional study of cardiac strain mapping over cardiac cycle. Studying the motion of the heart vis-a-vis the respiratory cycle and its variation amongst patient databases. Also interested in developing other novel approaches to noninvasive cardiac imaging.
Research Keywords
MRI, Cardiac, Strain, Noninvasive, navigators, nonbreathhold
