ABSTRACT
Mitral valve prolapse is a commonly described entity with a highly variable and benign course. However, it is associated with ventricular arrhythmias and sudden cardiac death in a small subset of patients. Recent studies have yielded insight into myocardial mechanics and the causation of ventricular arrhythmias in these groups of patients. Mitral annular disjunction (MAD) characterized by detachment of mitral annulus from left ventricular myocardium is associated with morphological and functional remodeling of the left ventricular myocardium. Resultant fibrosis acts as a substrate of ventricular arrhythmia and sudden cardiac death. We present two such cases of arrhythmic mitral valve prolapse associated with MAD. Cardiac magnetic resonance imaging provides excellent morphological information and also helps in the assessment of fibrosis.
ABSTRACT
Background Left ventricular ejection fraction (LVEF) is used as quantitative parameter to evaluate myocardial function. However, interobserver variation, limited reproducibility, and dependence on pre-load and after-load reduces its accuracy. The fall in LVEF occurs very late, when myocardial dysfunction is already advanced. Myocardial strain measurements (especially global longitudinal strain) is a new parameter to detect myocardial dysfunction before derangements in LVEF. The aim of this article is to share our experience of this novel diagnostic tool. Methods Feature tracking method of strain assessment is performed using routine long and short axis cine images of cardiac MRI (CMR). Dedicated post-processing CMR software can perform off-line analysis and provide results in form of color-coded maps, percentage values as well as strain over time curve for each myocardial segments. Results Global longitudinal strain (GLS) is more sensitive than LVEF and can identify sub-clinical left ventricular (LV) dysfunction in various cardiomyopathies. It is also an important prognostic marker in serial assessment of heart failure patients. Regional differences in strain parameters can provide clues in hypertrophic cardiomyopathy as well as amyloidosis. GLS is recommended as routine measurement in patients undergoing chemotherapy to detect LV dysfunction prior to fall in LVEF. Strain imaging can be applied to guide placement of the LV pacing lead in patients receiving cardiac resynchronization therapy. More clinical data is needed to evaluate its role in ischemic heart disease. Conclusion Strain imaging can identify LV dysfunction earlier than conventional methods and this opens a new perspective in risk stratification and therapeutic decision-making of various cardiac pathologies.
ABSTRACT
Impedance cardiography is a noninvasive technique, based on sensing the variation in the electrical impedance of the thorax caused by variation in the blood volume during the cardiac cycle, for monitoring the stroke volume and some other cardiovascular indices. Respiratory and motion artifacts cause baseline drift in the sensed impedance waveform, particularly during or after exercise. This paper presents an LMS-based adaptive filtering technique for suppression of respiratory artifact for improving the estimation of the indices without smearing the beat-to-beat variations. It uses a reference signal, closely related to the respiratory artifact, obtained by a least-squares approximation based B-spline fitting on the contaminated impedance cardiogram in synchronism with the respiratory phases. The technique is evaluated on signals with simulated artifacts and on signals from nine healthy subjects and five patients with cardiovascular disorders. The values of the stroke volume, estimated on beat-to-beat basis, after suppression of respiratory artifact showed a good agreement with those from Doppler echocardiography.
