Mohd Farid

Mohd Farid

Friday, October 21, 2016

MY RESEARCH PROPOSAL:P WAVE DISPERSION AND ITS ASSOCIATION WITH DIASTOLIC DYSFUNCTION IN ASYMPTOMATIC POPULATION OF THE URBAN AND RURAL MALAYSIA-Introduction Part I


P WAVE DISPERSION AND ITS ASSOCIATION WITH DIASTOLIC DYSFUNCTION IN ASYMPTOMATIC POPULATION OF THE URBAN AND RURAL MALAYSIA






MOHD FARID BIN MOHD TAUFIK






MSc




2016


Chapter One


INTRODUCTION 


1.1         INTRODUCTION


Atrial fibrillation (AF) enforce consequential concern of morbidity and impaired health related to general well-being of individuals, and extremely increases sufferer’s risk of obtaining a cardiovascular event, especially a stroke (apoplexy). Occurrence of atrial fibrillation in Asia and the associated medical care expenses are likely to have been underestimated and are required to improve due to increasing awareness, population ageing and higher prevalence of associated risks and comorbidities [1].

AF is the most persistent cardiac arrhythmia, and its occurrence in the population is increasing [2]. AF shares many common risk factors with left ventricular diastolic dysfunctio (LVDD), including age [3][4][5], hypertension [3][6][4][7], obesity [8],  and diabetes [9][10]. Patients given the diagnosis of LVDD are more likely to have AF at the time [11]. LVDD has significant pathological effects on atrial structure and atrial function especially LA, many are proarrhythmic that can induce arrhythmias such as AF. Nevertheless, there are so many aspects to be learned about the specific mechanisms through which LVDD induced development of AF [12].

There is growing understanding that congestive heart failure (CHF) caused by a significant LVDD that recognised as diastolic heart failure (HF). Common and causes significant morbidity and mortality is Diastolic HF [5]. Maintainance of sinus rhythm and normal atrial electrical conductions is vital for stability of cardiac output in individual with significant LVDD. Occurrence of AF causing atrial output to decreases. This will results in an increase of LVDD and progression of diastolic HF the patient’s clinical condition deteriorates [6].

There are many noninvasive electrocardiographic parameters have been applied to predict the occurrance of cardiac arrhytmias in individual with LVDD. It has been demonstrates that P wave dispersion as a noninvasive parameter that enables the evaluation of AF risk on the 12 lead surface ECG. This is because of its association to the nonhomogenous and interrupted conduction of sinusal electrical impulses both intra-atrially and inter-atrially [13][14].

LVDD is an important risk factor of AF, because LVDD has fundamental pathological influences on atrial structure and atrial function. Vranka et al. [15] attempted to determine how LVDD increases LAP and LA diameter, both of which influence atrial conduction times measured noninvasively by electrocardiography of P wave.

Researcher will investigate the association between P wave dispersion and the presence of LVDD as detected by Doppler echocardiography, the stage, origin, and other echocardiographic indicators of LVDD that includes LA volume, LA volume index, LA dimension, LA active emptying fraction, LA total emptying fraction and other echocardiography parameters that can represent performance of LA in individual with asymptomatic AF, individual with type 2 diabeties melitus (DM), individual with hypertension and individual that is  asymptomatic healthy individual.

1.2         PROBLEM STATEMENT


P wave dispersion can be used in predicting the risk of AF [13] in LVDD patient. Gunduz et al. [16] in their finding noted that the presence of LVDD is an important factor affecting P wave duration. The goal of the proposed study is to investigate association between LVDD, P wave dispersion and AF. 

P wave measurement by 12 lead ECG have been stated to be applicable tools for assessing the risk of LA enlargement and LVDD [16][17]. Gunduz et al. [16] in their finding noted that prolongation in P wave dispersion is related to LA diameter or to stage of LVDD. Gunduz et al. [16] in their finding also noted as LVDD stage of patient progressed, LA dimensions increased significantly. However, Dilaveris et al. [13] have found that LA diameter is not an important predictor for AF and that P wave duration is unrelated to LA diameter. The purpose of the proposed study is to determine the effect of LVDD on LA diameter and its association with P wave dispersion.

Earlier Tsang et al. [18] have done an early study to examine LVDD and incident AF. They followed 840 elderly men and women, of whom 80 (9.5%) developed atrial fibrillation over a average follow up of 4.1 years. With the use of a derived classification system for LVDD based on transmitral Doppler patterns and LA volume index. They found that more severe LVDD was related with an elevated risk of AF incident. Tsang et al. [18] in their study of 840 elderly men and women also suggest that the strongest predictor of AF was LA volume index.

Later Tsang et al. [19] have done follow-up study that examined only patients with impaired relaxation based on transmitral peak E/A (0.75) and deceleration time (240ms) and found an increased risk of the combined outcome of AF and HF with impaired relaxation, although this effect was not significant in the absence of an increased LA volume index (27 mL/m2). This finding again suggesting that it was LA size, rather than any particular diastolic parameter, that increases risk of AF. In addition, normal LA volume in a patient with advanced LVDD is most unusual unless the LV filling pressure increase abruptly because of the sudden onset of a structural abnormality, such as severe mitral regurgitation or aortic regurgitation due to sudden valvular disruption or valvular abnormalities. LA volume is a good predictor of the development of AF and long term outcome in various cardiac disorder [19]. The purpose of the proposed research is to determine the effect of LVDD on LA volume and LA volume index and its association with P wave dispersion.

Faggiano et al. [20] in their study show the relationship between LAP or pulmonary capillary wedge pressure (PCWP) obtain by right sided heart catheterization and obtain by echocardiography to signal averaged P wave duration in patients with CHF. The author believes that in patients with chronic HF, P wave duration in signal average ECG seems to depend more on the level of LAP compare to LA dimension. Vranka et al. [15] supports Faggiano et al. [20] with their result that high left atrial pressure expressed by increased E/E’ ratio, may be play an important role in prolonging P wave duration, as was shown by Doppler parameters. The author suggest that prolonged atrial conduction was not associated with LA enlargement. The goal of the proposed study is to examine association between LVDF and its effect on P wave dispersion and LA.

Morris et al [21] mentions that individuals with HF with normal LVEF had more impaired LA systolic function compared to asymptomatic population. The author states that noninvasive LV filling pressure were modestly related with LA systolic function. The goal of the proposed study is to investigate association between LVDD and its effect on P wave dispersion and LA systolic function.
In essential hypertension in adult individuals, a significant relationship has been showed between changes in LV geometry and P wave dispersion.  P wave dispersion is the difference between maximum and minimum P wave duration measured on 12 lead ECG [13]. Hypertension is one of the causes of AF. LVDD in a hypertrophic LV results in an increase in LV end diastolic pressure and in LA dimension [22]. De Marchi et al. [23] showed an important association between the extent of hypertrophy and LVDD. The target of the proposed study is to examine the relationship between LVDD, LV hypertrophy, P wave dispersion and its effect on LA dimension, LA volume and LA volume index in hypertensive population.

Patil and colleagues [10] in their finding stated that preclinical LVDD is common in patient with DM. Soldatos et al. [24] in their case control study of individuals with Type 2 DM found that LVDD, present in a significant proportion with Type 2 DM. Boyer et al. [25] stated that the prevalence of LVDD in asymptomatic, normotensive patients with Type 2 DM disease is high. Yazici et al. [26] also manage to show that prolongation of P wave dispersion can be seen in Type 2 DM cases without hypertension and ischemic heart disease. They found that slightly prolong P wave dispersion in the Type 2 DM group compare to the control group but diastolic relaxation parameters, such as early diastolic rapid filling and isovolumic relaxation time (IVRT) were within normal value and mean LA diameter were similar in both groups. Depends on these findings, P wave dispersion is not affected by these diastolic parameters. The aim of the proposed study is to examine the relationship between LVDD, LV hypertrophy, P wave dispersion and its effect on LA dimension, LA volume and LA volume index in diabetic population.


1.3         OBJECTIVES


1.3.1        Main Objective


To investigate association between Left Ventricular Diastolic Dysfunction (LVDD), P wave dispersion and AF.


1.3.2        Objectives


1.      To investigate association between LVDD and its effect on P wave dispersion, LA dimension, LA volume and LA volume index.

2.      To investigate association between LVDD and its effect on P wave dispersion, LA systolic function and LAP.

3.      To examine the effect of LVDD on LA dimension, LA volume, LA volume index, LA systolic function and LAP with presence of increased P wave dispersion compared to healthy controls.

4.      To examine the effect of LVDD on LA dimension, LA volume, LA volume index, LA systolic function and LAP with presence of increased P wave dispersion compared to hypertensive population.

5.      To examine the effect of LVDD on LA dimension, LA volume, LA volume index, LA systolic function and LAP with presence of increased P wave dispersion compared to diabetic population.

1.4         RESEARCH QUESTION


Does prolonged P wave dispersion cause AF?What is the relationship between P wave dispersion and LVDF?

3.      What is the association between LVDD and its effect on P wave dispersion, LA dimension, LA volume and LA volume index?

4.      What is the association between LVDD and its effect on P wave dispersion, LA systolic function and LAP?

      What is the effect of LVDD on LA dimension, LA volume, LA volume index, LA systolic function and LAP with presence of increased P wave dispersion compared to healthy controls?

What is the the effect of LVDD on LA dimension, LA volume, LA volume index, LA systolic function and LAP with presence of increased P wave dispersion compared to hypertensive population?

What is the the effect of LVDD on LA dimension, LA volume, LA volume index, LA systolic function and LAP with presence of increased P wave dispersion compared to diabetic population?

1.5         RESEARCH HYPOTHESIS



1.      Normal P wave duration, LVDD, LA dimensions, LA area, LA volume, LA volume index, LA active emptying fraction and LA total emptying fraction in control group.

2.      Prolong P wave duration and dispersion in study group with hypertension.

3.      Prolong P wave duration and dispersion study group with type 2 diabetes mellitus.

4.      Prolong P wave duration and dispersion with evidence of LV hypertrophy in study group with hypertension and diabetes mellitus.

5.      The LVDD worsens in study group with hypertension.

6.      The LVDD worsens in study group with type 2 diabetes mellitus.

7.      LA dimensions, LA area, LA volume, LA volume index and LAP were significantly increased in study group with hypertension.

8.      LA dimensions, LA area, LA volume, LA volume index and LAP were significantly increased in study group with type 2 diabetes mellitus.

9.      LA active emptying fraction and LA total emptying fraction were significantly reduced in study group with hypertension.

10.  LA active emptying fraction and LA total emptying fraction were significantly reduced in study group with type 2 diabetes mellitus.

1.6         SIGNIFICANCE OF THE STUDY


AF is the most common persistent cardiac arrhythmia, and increasing in prevalence. AF occurs in 0.3% to 0.4% of the adult group [9]. The impact of AF on morbidity and mortality is high. It will give socioeconomic burdened to the society. AF is most commonly seen in patients with underlying structural heart disease, including hypertensive population, cardiomyopathy, ischemic heart disease, valvular heart abnormalities and HF [27].

Early identification of patients at risk of AF may help to reduce potential health risks, costs and other related complications. P wave dispersion analysis has been shown to classified between individuals at risk of AF and those without risk of AF. P wave prolongation on may be associated with left ventricular diastolic dysfunction and following an increase of LAP, LA enlargement and reduced LA systolic function; therefore, P wave  prolongation should be assessed in individuals at risk of AF. Combining P wave duration with other predictors of AF may improve the diagnostic value of P wave dispersion analysis [15].

In condition of ncreased in LV end diastolic pressure with LVDD, the maintainance of normal sinus rhythm and atrial contractions is essential for the maintainance of cardiac output. If AF occurs, the loss of efficient atrial contraction, which accounts for 40% of atrial output during diastolic phase. This will results in worsening of LVDD and in progression of diastolic HF [6].

Identifying association of P wave dispersion with early echocardiographic changes especially on LVDF assessment allow physicians to intervene and manage underlying illnesses more aggressively to reduce risk of development of AF. Potential health risk such as hypertension and Type 2 DM nowadays have increasing in Malaysia population has been proved to be risks factors of LVDD and P wave dispersion. Early treatment of this potential risk can also reduced risk of developing AF.

1.7         DELIMITATIONS OF THE STUDY


The study will be limited to an investigation of respective knowledge specifically on non invasive LVDD evaluation by 2D echocardiography and Doppler echocardiography modalities analysis. The study also will be limited to an investigation of respective knowledge on non invasive 12 lead surface ECG analysis specifically on P wave characterictic. Invasive LVDD and intra cardiac electrophysiology study evaluation will not be obtain and tested.

1.8         LIMITATIONS OF THE STUDY


The LA function will only focusing on systolic function. Left atrial diastolic function evaluation has to be done by strain imaging. Strain imaging did not included in raw database to be obtain, test and evaluate. 

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