Introduction to Biventricular pacing (BVP)
Biventricular pacing (BVP) or cardiac resynchronization therapy (CRT) is a therapy that is used in patients that are suffering for severe refractory failure of heart despite management by optimal use of medicines (Li and et.al., 2013). It is very beneficial for patients that have a non reversible kind of systolic heart failure, a poor functioning of left ventricle along with ejection fraction less than 30 percent and an evidence of ventricular dissynchrony (Jiang and et.al., 2013).
The aim of this technique is to make patients derive several benefits related to morbidity, mortality and increased quality of life. The basic theory behind its usage is to meet the specific needs of individual patient in such a manner that non responder or suboptimal user will derive increased benefit. The present report from assignment desk will try to make a thorough comparison of current practice method for Echocardiography Biventricular optimization that is used in current department with the articles.
The search strategy in present study will involve for going through the Cochrane Library, Pub med literature, EMBASE and Science Direct search by using terms like cardiac resynchronization therapy, CRT, Biventricular pacing, BVT, Echocardiography Biventricular optimization as well as heart failure. The terms have been searched in title, key words and abstract. Only that literature has been selected that is relevant to given research topic. It has been made sure that articles that have been selected are not older than ten years. However, a flexibility is considered if the article is found to be relevant and completely apt with the study. But in that case, articles are not older than 2001. Key articles have further been selected for this method review.
History of How the Method was Chosen
Failure of heart happens to be a significant problem in UK where there is an increased level of morbidity and mortality associated with failures in heart. There is a poor quality of life as well as recurrent hospitalizations in heart patients (Fox and et.al., 2013). This has resulted in a survival rate of less than 4 years in 50 percent of the cases. Varied methods have been used to reduce failure of heart. In this regard, Synchronized atriobiventricular pacing has provided for acute hemodynamic improvements and symptomatic benefits inclusive of overall life quality followed by reduction in hospital admissions (Grimm and et.al. 2008).
The COMPANION study has suggested towards a trend where there has been a reduction in mortality rate by 24 percent with biventricular pacing in comparison to optimal medical therapy. The mortality benefit has further been 36 percent in biventricular pacemaker-defibrillator. There has also been a presence of additional protection from malignant ventricular arrhythmias (Lane and Mayet, 2013).
Disorders For Which The Analysis/investigation May Be Used
The disorders for which Echocardiography Biventricular optimization is used are dilated cardiomyopathy, bundle branch block, class III and IV systolic heart failure, cardiac amyloidosis.
For treating patients with dilated cardio myopathy, Echocardiography Biventricular optimization is a promising technique. This is because of resynchronization of LV activation. Biventricular pace maker that is capable of stimulating both the ventricles simultaneously (Oh, Seward and Tajik, 2006). By early activation of the left ventricular free wall, biventricular pacing helps in improving the hemodynamic. Cardiac resynchronization therapy works by stimulating both the ventricles at the same time.
Contraction of ventricles is achieved which improves the efficiency of heart and thus condition of patients suffering from dilated cardiomyopathy. There occurs substantial improvement in the cardiac functions and symptoms. Dilated cardiomyopathy is characterized by overall weakening of the muscles of heart and poor contraction (Hutchison, 2012). The pattern of contraction of heart becomes abnormal. This is because half of the heart pumps while the other half does not. CRT helps in re-timing the heart. This results in synchronous pumping of both the sides. With this it has been observed that symptoms of heart failure improve.
The efficacy of cardiac resynchronization therapy though biventricular pacing has been demonstrated by numerous studies in patients who suffer from left branch bundle block. Echocardiography is used for studying the systolic and diastolic ventricular function. Left branch bundle block is considered as a risk factor for progression to the failure of heart (Zannad and et.al., 2007). It is an abnormality in the cardiac conduction. This condition is characterized by delayed activation of the left ventricle. As a result, the contraction of the left ventricle occurs later than the right ventricle. Biventricular pacing benefits the patients with left branch bundle block who have a markedly prolonged QRS that is usually greater than150 ms (Garcia, 2012). This is because this allows better synchrony of the contractions of heart.
Evaluating Sensitivity and Suitability
The given method being Echocardiography Biventricular optimization is being used for treating heart failure. Hence, the requirement is to carry out a thorough evaluation on sensitivity and suitability for screening the presence of disorders verses identification of disorder variants. Studies have clearly depicted that usage of Echocardiography Biventricular optimization have brought a substantial reduction in mortality and overall level of hospital admission related to heart failure. There has also been an improvement in overall quality of life in patients suffering from class III and IV heart failure. In this respect, the study carried out by Mortensen and et.al. 2004 have clearly revealed that usage of INSync3 biventricular stimulator is very safe and effective. This is especially true in case of the patients who have been suffering from symptomatic systolic heart failure as well as prolonged form of QRS complex duration (Mortensen and et.al. 2004). The study by Vanderheyden and et.al. 2005, have also revealed that CRT as a technique can further be helpful to track the progress of responses for an individual patient (Vanderheyden and et.al. 2005).
Methods to Describe the Nature of the Disease
Myocardial performance index is useful in indicating the global myocardial performance. The elements of systole and diastole are incorporated in it. This index can be used as method for assessing the conditions where systolic and diastolic dysfunctions coexist. Indices of left ventricular systolic and diastolic function are predictors of subsequent heart failure. This index is the sum of isovolumic contraction tome and isovolumic relaxation time divided by the relaxation time. The pre ejection period is lengthened while the ejection time is shortened as a result of left ventricular systolic dysfunction (Kato and et al, 2005). As a result of this, there occurs an increase in the pre ejection period to ejection time ratio.
Through all the stages of diastolic dysfunction, there occurs an increase in the value of time constant of left ventricular relaxation. As a result of this, prolongation of isovolumic relaxation time takes place with abnormal relaxation. In order to compensate for the increased left ventricular filling pressure there occurs shortening of ejection time with premature closure of mitral valve and prolongation of isovolumic contraction time. As a result of this, MPI increases. Hence, MPI clearly indicates the nature of heart failure that is associated with systolic dysfunction, diastolic dysfunction or a combination of the two (Klabunde, 2013).
- Abraham, T. W. and Hayes, L. D. (2003) ‘Cardiac Resynchronization Therapy for Heart Failure.’ Circulation, 108. Pp.2596-2603.
- Altman, R. K., and et.al. (2012) ‘Multidisciplinary care of patients receiving cardiac resynchronization therapy is associated with improved clinical outcomes.’ European Heart Journal, 33. Pp. 2181–2188.
- Bansch, D. and et al. (2002) ‘Primary prevention of sudden cardiac death in idiopathic dilated cardiomyopathy: the Cardiomyopathy Trial (CAT).’ Circulation, 105. Pp.1453-1458.
- Chinen, D. and et.al. (2013) ‘Left ventricular outflow tract velocity time integral correlates with low cardiac output syndrome in patients with acute decompensated heart failure.’ European Heart Journal, 34(1).
- Chung, E. S. and et al. (2008) ‘Results of the predictors of response to CRT (PROSPECT) trial.’ Circulation, 117. Pp.2608–2616.