Background:

While left ventricular ejection fraction (LVEF) is commonly used in guidelines to direct treatment, it is limited by the inability to detect dysfunction before damage occurs.  Since the heart is able to compensate for some regional dysfunction to maintain cardiac output, traditional measures such as LVEF only detect dysfunction when substantial damage produces symptoms. Fast-SENC segmental intramyocardial strain (fSENC) is a unique cardiac magnetic resonance imaging (CMR) modality that directly measures myocardial contraction.  By detecting subclinical dysfunction, fSENC augments treatment to avoid damage and heart failure instead of simply managing symptoms.  This prospective registry compares fSENC and LVEF in various cardiac diseases.

Methods:

A single center, prospective registry was collected from patients with fSENC acquired with a 1.5T MRI scanner (Philips) and processed with the MyoStrain software (Myocardial Solutions). fSENC directly measured intramyocardial strain across 37 longitudinal and circumferential segments to quantify the % normal myocardium (fSENC < -17%). Segmental fSENC was compared to LVEF and other traditional CMR measures for a variety of cardiac diseases.

Results:

fSENC and traditional CMR measures were obtained during 674 scans in 537 subjects.  Patients had an average stdev age of 53 ±16 yrs; 45% had arterial hypertension, 11% diabetes mellitus, 29% valvular heart disease, 7% atrial fibrillation, and 22% coronary artery disease; 4% had left bundle branch block (LBBB), 5% had dilated cardiomyopathy (DCMP), 17% had myocarditis (MYO).

                                A                                                                          B                                                                    C


Figure 1 (A to C) shows the relationship between % normal myocardium (fSENC < -17%) and LVEF in patients with LBBB, DCMP and MYO respectively.  Best-fit polynomial curves were calculated for each disease (r = 0.9) and the total study population (r=0.77).  The response of LVEF to fSENC depended on the ability of the heart to compensate for segmental dysfunction for each disease.  However, the severity of the disease and response to medications were consistently quantified with fSENC.


Conclusion:

fSENC detects subclinical dysfunction before symptoms or reduction in LVEF.  Even in patients with normal LVEF and global measures, fSENC quantifies the progression of structural heart diseases and the impact of drug or device therapies.