Diagnostic Utility of Electrocardiogram and Transthoracic Echocardiography in Diagnosis of Left Ventricular Hypertrophy among Known Hypertensive Patients

The purpose of the study is to find out presence of LVH by 2D Echo in all cases of hypertension in relation to their duration and severity. In this study it was observed that 59% subjects were males and 41% were females and the mean age of males and females was 64 yrs. Majority of them 36.5% were in the age group of 61-70 yrs, out of them majority of females 48.6% were from age group 71-80 yrs and majority of males 76.5% were from age group of >80 yrs. Study showed that occurrence of LVH by Interventricular septal thickness criteria and Left ventricular posterior wall thickness criteria of 2D Echo in relation to duration of hypertension was statistically not significant. Occurrence of LVH by interventricular septal thickness criteria and Left ventricular posterior wall thickness criteria of 2D Echo in relation to severity of hypertension was statistically not significant.


INTRODUCTION
A variety of cardiovascular disorders are characterized by left ventricular hypertrophy (LVH). CAD is one of the most common causes of death in developed and developing countries. Hypertension is one of the main risk factors for CAD [1,2]. Hypertension is present in three of four patients with CAD. The development of LVH increases with the severity of hypertension. LVH is associated with systolic and diastolic function abnormalities, ventricular arrhythmias which are one of the causes of sudden cardiac death among hypertensive and hence LVH is an independent predictor of morbidity and mortality. Limited resources and high cost of maintenance make availability of ECHO facilities infeasible for many centers in developing countries like India. Though ECHO is superior to ECG, it is costly and it demands considerably more time, technical skill of the operator and complexity of processing than routine 12 lead ECG. Hence it is important to study the reliability of ECG in diagnosis of hypertension patients. The purpose of this study is to determine the reliability of ECG in diagnosis of LVH by its correlation with 2 D Echo in patients of hypertension.

Aim
To study the diagnostic utility of electrocardiogram and transthoracic echocardiography in diagnosis of left ventricular hypertrophy among known hypertensive patients.

Objectives
To find out presence of LVH by 2D Echo in all cases of hypertension in relation to their duration and severity. To study specificity & sensitivity of diagnosis of LVH by ECG as compared to 2D Echo with different ECG criterias. To assess diastolic dysfunction in patients with hypertension with echo proven LVH.

Review of literature
Stephen Hales (1733), in eighth century clergyman and pioneer of experimental physiology measured BP for the first time in horses. The height of column of blood in a vertical tube inserted into an artery denoted the BP [3]. In 1886 Riva Rocci invented the pneumatic compression cuff to measure the BP.
In 1905, NS Korotkoff, a Russian Physician described Korotkoff sounds and later Erlanger (1921) put forward the concept of muffling of sounds.
Linzbach (1960) [4] stated that there is an indirect evidence that the number of myocardial cells may increase during hypertrophy in an adult individual.
Meerson (1969) [5] had stated that heart has a good capacity to undergo hypertrophy in response to the abnormally increased work load which he termed as a compensatory hyperfunctioning of the heart.
Benzak (1969) [6] showed experimentally that myocardial cells return to their original size when the cardiac work load is returned to normal.
Legato (1970) [7] had provided electron microscopic evidence suggesting that the 'Z' line substance is essential for new sarcomeres production during cardiac hypertrophy.
Devereveux R. Richek. N (1986) [8] calculated LV mass by ECHO using Penn convention method and correlated this work with angiographic studies.
Daholf B (1992) [9] had shown in a meta analysis of various studies that there is a reversal of LVH in the hypertensive patients after regular treatment with antihypertensive drugs which can be studied by ECG and ECHO.  [11] that there is relationship between LV mass and hypertension once the hypertension diagnosed and treated. They assessed LVH by ECG which was correlated with LV mass assessed by Echo. They found that the Echo parameters of LV mass in hypertensive subjects correlated better when compared with ECG parameters of LVH in patients with hypertension.
While setting standard values of mitral influx velocity as well as time intervals, age is a key factor. The velocity of mitral inflow and E/A-ratio decline as many factors apart from the LV diastolic activity as well as filling constraints affects mitral influx, and also PR interval as well as heart beat rhythm and rate. Variations in variables of age-related cardiac output can slow down and potentially expose elderly people to the progression of diastolic dysfunction.

MATERIALS AND METHODS
All patients having hypertension without type 2 Diabetes Mellitus, chronic kidney disease, thyroid dysfunction, hepatic dysfunction, congenital heart disease and left ventricular systolic dysfunction above age of 40 yrs during the period of 18 months (1st Oct 2014 to 31st March 2016) will be included in the study. All these patients ECG and 2D Echo will be done and studied for LVH according to duration and severity of hypertension. All hypertensive patients above age of 40 yrs both IPD and OPD will be included.

OBSERVATION & RESULTS
Eighty two patients (41%) out of 200 had LVH and 118 (59%) had no LVH according to Sokolov-Lyon criteria of ECG. (Table 1).  (Table 3). ECG LVH seems distinctive from echo LVH from a structural point of view (Fig. 1). For instance, when there is no considerable rise in LV mass, the myocyte hypertrophy to the degree identified in ECG LVH is highly unlikely to be seen in isolated Echo LVH. However, ECG LVH is related to a higher risks for ventricular and atrial irregularities. The higher incidence of ventricular arrhythmias in ECG LVH patients is related to hypertension. With increased left ventricular mass, the magnitude as well as severity of arrhythmia increases with an increasing arrhythmia of 2-3 times over 1mm within the left ventricular wall thickness [12].  (Table 4).

CONCLUSION
Though ECG is the baseline/simple, cheaper, easily available means to study cardiac diseases, to study for LVH in hypertensive patients it is less sensitive and more specific. It has to be further evaluated with 2 D Echo. ECG criterias (Sokolov-Lyon index, Romhilt-Estes Point Score and Cornell-Voltage Criteria) have low sensitivity but high specificity than 2D Echo in diagnosis of LVH. And hence these methods have a limited use as a screening test of LVH. ECG can still be recommended as a routine investigation for diagnosis of LVH because of its cost effectiveness and easy availability but should not be used to rule out LVH. Majority of patients having diastolic dysfunction was detected in stage 1. Hence it is important to screen for diastolic dysfunction in patients with LVH, which is again a risk factor for further cardiac dysfunction.

CONSENT AND ETHICAL APPROVAL
As per university standard guideline, participant consent and ethical approval have been collected and preserved by the authors.