J. Exp. Biomed. Sci. 2011, 17(2): 141~149 Difference of The Cardiac Structure and Function Depending on Obesity Level of Healthy Adults Kyung-A Shin 1, and Seung-Bok Hong 2 1 Department of Laboratory Medicine Bundang Jesaeng Hospital, Sungnam-si, Gyeonggi-do 463-774, Korea 2 Department of Clinical Laboratory Sciences, Juseong University, Cheongwon 363-794, Korea The purpose of this study was to find out any difference and correlation between the cardiac structure and its function according to the level of obesity as evaluated by waist measurement and BMI (body mass index) in healthy adults. For research subjects, the study selected a final 519 subjects excluding 198 subjects aged 55 or over out of 717 subjects who received echocardiography through a medical checkup at J General Hospital. For the criteria for obesity, men were defined as being obese in case their waist measurement was over 90 cm, whereas women were defined as being obese in case their waist measurement was over 80 cm. Also, regarding the BMI criteria, in case a person's BMI was 30 kg/m 2, the subject was classified as belonging to an obese group, and in case a person's BMI was between 25 kg/m 2 and 30 kg/m 2, the subject was classified as belonging to an overweight group. Concerning the evaluation of cardiac structure and function, they were evaluated using two-dimensional, M-mode, doppler echocardiography. According to the stage of obesity in accordance with waist measurement and BMI, the cardiac structure showed both eccentric and centripetal changes, and the cardiac function was also discovered to show differences according to the stage of obesity. In addition, also in the overweight group, which is a prior stage to obesity, out of the criteria for obesity classification according to BMI, there were differences in the cardiac structure and function. Also, both the waist measurement and BMI were found to have a correlation with cardiac structure and diastolic function. Consequently, cardiac structure and function are correlated with BMI and waist measurement, which are anthropometrical variables, and obesity is assumed to induce not only structural change but also functional change of the heart. Key Words: Obesity, Waist circumference, BMI, Cardiac structure, Cardiac function 서 최근우리나라는운동부족과식생활의서구화로인해비만인구가급격한증가를보이고있으며, 비만은고혈압, 제 2형당뇨병, 이상지질혈증및심혈관질환을증가시키는위험요인으로알려져있다 (Massie, 2002; Haslam & James, 2005). 비만과심혈관질환의직접적인관련성에대해좌심실벽두께, 심방크기, 좌심실질량과같은심장구조와수축기및이완기기능의비정상성과관련이있는것으로보 * 접수일 : 2011년 5월 2일 / 수정일 : 2011년 5월 31일채택일 : 2011년 6월 10일 교신저자 : 신경아, ( 우 ) 463-050 경기도성남시분당구서현동 255-2, 분당제생병원진단검사의학과 Tel: 010-2759-8672, Fax: 031-779-0257 e-mail: mobitz2@hanmail.net 론 고되고있다 (Lauer et al., 1991; Peterson et al., 2004b; Wong et al., 2004; Avelar et al., 2007). 또한좌심실비대와같은심장구조의변화와수축기및이완기기능의변화는심혈관질환의독립적인위험요인으로알려져있으며 (Levy et al., 1990), 그기전으로는비만에따른혈압의상승, 인슐린저항성, 심근대사의변화, 염증성사이토카인 (inflammatory cytokines), 혈관내피기능장애등으로알려져있다 (Zhou et al., 2000; Mavri et al., 2001; Aasum et al., 2003; Engeli et al., 2003; Esposito et al., 2003; Peterson et al., 2004a; de las Fuentes et al., 2005; Arkin et al., 2008). 체질량지수 (body mass index, BMI) 에의한과체중과비만 ( 의 ) 기준은세계적으로가장널리이용되는비만지표로서심혈관질환에의한사망률의예측인자이며 (Flegal et al., 2005; Yan et al., 2006), 심장기능의비정상성은전체비만을반영하는체질량지수및비만기간과정의상관관계가있다 (de Simone et al., 2005; Krishnan et al., 2005; - 141 -
Domanski et al., 2006; Dorbala et al., 2006). 또한비만은만성적혈액용적의증가 (chronic volume overload) 로인해심근증 (cardiomyopathy) 을유발하게되며 (Di Bello et al., 2006), 체질량지수와도플러심초음파를통한좌심실이완기기능변화를알아본결과체중증가에따라좌심실수축기장애에선행하여이완기기능장애가나타난다 (Ryu et al., 2008). 그러나최근에는비만을나타내는지표중에서복부지방의분포가체질량지수보다대사성위험인자를더잘반영하는것으로밝혀졌으며, 그중허리둘레는내장지방뿐아니라심혈관질환의위험과높은관련성을나타내면서심혈관질환을예측하는데체질량지수보다더효과적인것으로인식되었다 (Jassen et al., 2004). 또한고혈압환자를대상으로비만도가좌심실이완장애에미치는영향에대한연구에서체질량지수에의한비만기준보다복부비만이좌심실이완장애와더밀접한관련이있는것으로보고되었다 (Kim et al., 2006). 이러한결과는체질량지수는정상이면서복부비만이많은아시아인에게서지방분포가심혈관질환을평가하는하나의지표로고려되어야함을의미한다 (Yusuf et al., 2005; Ryu et al., 2008). 이러한중요성에도불구하고국내에서는복부비만과심장의구조및기능과의관련성에대한연구가미흡한실정이다. 또한비만을판정하는기준에따라비만의분류가다를수있기때문에본연구에서는합병증이없는건강한성인을대상으로허리둘레와체질량지수로평가된비만정도에따라심장구조및기능의차이와관련성에대해조사하였다. 재료및방법대상이연구의대상은 2009년 11월부터 2010년 12월까지경기지역 J 종합병원에서건강검진을통해심초음파를실시한 717명을대상으로하였으며, 심장기능은연령과상관관계가있으므로 (Ryu et al., 2008), 55세이상의피험자 198명을제외한 519명을최종대상자로하였다. 비만기준중허리둘레기준은아시아태평양지역의비만기준 (Asia-Pacific Criteria: APC) 에따라남성의경우는 90 cm 이상, 여성은 80 cm 이상으로정의하였다 (WHO, 2000). 또한체질량지수기준은 30 kg/m 2 이상인경우비만군, 25 kg/m 2 이상 30 kg/m 2 미만인경우과체중군으로 정의하였다 (WHO, 2000). 뇌, 심혈관질환자로지질대사에영향을미치는지질합성억제제와같은약물복용또는경흉부심초음파결과좌심실구혈율이 55% 이하, 대동맥판막또는승모판막질환이있는경우, 협심증증상이있는경우는제외하였다. 이연구는 J 종합병원의임상시험윤리위원회승인을받았으며, 연구대상자들에게연구목적과방법에대해설명하고서면동의서를받았다. 심장구조및기능평가 심장초음파검사는모두동일한검사자가시행하였고, Sonos 5500 (Hewlett-Packard Co., U.S.A) 심초음파장비를이용하여대상자를검사용침대에앙와위로눕힌자세에서 2.5 MHz 탐촉자를피험자의좌경흉부에대고흉골연장축단면도, 단축단면도, 심첨부단면도를시행하였다. 이면성, M-mode, 도플러심초음파검사를시행하였고, 모든검사내용은비디오테이프에기록하였다. 이면성, M-mode 심초음파검사는미국심초음파학회 (American Society of Echocardiography Committee on Standard: ASE, Table 1. The clinical characteristics of subjects on the basis of waist circumference Variables Normal (n=417) Obese (n=102) Age (years) 43.2±6.8 45.1±6.7 ** Male (%) 268 (64.3) 69 (67.6) Height (cm) 166.8±10.9 169.1±8.1 * Weight (kg) 64.4±10.5 78.9±12.0 *** BMI (kg/m 2 ) 22.9±2.7 27.4±2.8 *** Muscle mass (kg) 45.5±8.5 51.2±9.9 *** % body fat (%) 24.1±9.3 29.8±11.1 *** Systolic BP (mmhg) 108.5±12.7 117.4±16.3 *** Diastolic BP (mmhg) 70.1±10.3 77.5±11.2 *** HDL-cholesterol (mg/dl) 56.6±14.0 50.0±10.4 *** LDL-cholesterol (mg/dl) 121.0±30.3 131.4±30.6 ** Total cholesterol (mg/dl) 196.9±32.9 204.5±33.0 * Triglyceride (mg/dl) 117.6±69.4 154.9±76.5 *** Glucose (mg/dl) 91.4±16.7 101.9±26.8 *** HbA1c (%) 5.6±0.6 6.0±1.0 *** Insulin (μu/ml) 4.6±2.6 6.9±3.3 *** hs-crp (mg/dl) 0.14±0.31 0.23±0.47 Values are Mean ± SD. ***, P<0.001; **, P<0.01; *, P<0.05 (compared with Normal group). Abbreviation: BMI, body mass index; BP, blood pressure; HDL, high density lipoprotein; LDL, low density lipoprotein; HbA1c, hemoglobin A1c; hs-crp, high sensitivity C-reactive protein. - 142 -
1989) 에서제시하는표준화된방법으로측정하였다. 좌심실질량 (left ventricular mass: LV mass) 은 cube formula 를이용한 corrected ASE method로계산하였고, 이를체표면적 (body surface area: BSA) 으로나누어좌심실질량지수 (LV mass index) 를구하였다. 심장의이완기능측정은 pulsed wave Doppler 심초음파를이용하여승모판막소엽의끝에서이완기초기승모판혈류속도 (E-velocity), 이완기후기승모판혈류속도 (A-velocity), E/A 비율, 초기이완기최대혈류감속시간인 E파의감속시간 (deceleration time: DT) 을측정하였다. Tissue Doppler 심초음파를이용하여초기승모판륜혈류속도 (E'-velocity) 를측정하여 E/E' 비율을구하였다. 신체계측및체성분분석신장및체중은자동신장 체중계 (SH-9600A, Sewoo system, Korea) 를사용하였으며, 체질량지수는체중 (kg)/ 키 (m 2 ) 의공식으로구하였다. 허리둘레는직립자세에서허리가완전히노출되게한후최하위늑골하부와골반장골능과의중간부위를측정하였다. 혈압은 10분간안정상태에서수은혈압계를이용하여측정하였으며, 신체구성측정은생체전기저항분석법 (Bio-electrical impedance analysis) 을이용한 Inbody 4.0 (Biospace, Korea) 을사용하여공복상태로측정하였다. 대상자는기계의전극발판에맨발을댄상태에서직립자세를취한후전극손잡이를몸통에서 30 cm 정도벌리고잡았다. 8점터치식전극법 (8-point tactile electrode), 다주파수분석법 (multi-frequency analysis) 을이용해인체부위별전기저항을측정하여근육량 (muscle mass), 체지방량 (body fat mass) 을산출하였다. 혈액검사혈액측정은 8시간금식후아침에채혈을실시하였다. TBA-200FR (Toshiba, Japan) 을이용하여 hs-crp (high sensitivity C-reactive protein), HDL 콜레스테롤, LDL 콜레스테롤, Total 콜레스테롤, 중성지방, 공복혈당을측정하였으며, 당화혈색소 (hemoglobin A1c) 의분석은 Variant II (Bio Rad, U.S.A) 를이용하여 HPLC (high performance liquid chromatography) 법으로측정하였다. 인슐린은 ADVIA centaur (Siemens Healthcare Diagnostics, Los Angeles, CA, U.S.A) 로 direct chemiluminescence 법을이용하여 two-site sandwich 법을원리로측정하였다. Variables Table 2. The clinical characteristics of subjects on the basis of BMI Normal (n=322) - 143 - Overweight (n=172) Obese (n=25) Bonferroni Age (years) 42.7±7.1 45.1±6.1 44±6.0 A<B ** Male (%) 178 (55.3) 140 (81.4) 19 (76.0) Height (cm) 166.0±11.8 170.0±7.2 170.4±8.2 A<B ** Weight (kg) 60.9±8.9 75.7±7.9 90.8±10.3 A<B<C *** Waist circumference (cm) 75.0±7.6 85.9±6.0 96.1±5.5 A<B<C *** Muscle mass (kg) 43.3±7.9 51.1±7.8 57.5±8.9 A<B<C *** % body fat (%) 23.5±10.3 27.5±9.2 31.5±4.7 A<B<C *** Systolic BP (mmhg) 106.7±12.6 114.7±13.5 124.4±15.8 A<B<C *** Diastolic BP (mmhg) 68.9±10.2 75.1±10.2 81.0±11.6 A<B<C *** HDL-cholesterol (mg/dl) 58.7±13.9 50.4±11.8 46.5±6.9 A, B>C *** LDL-cholesterol (mg/dl) 118.2±29.5 131.7±31.1 126.4±29.7 A<B *** Total cholesterol (mg/dl) 194.4±32.5 205.6±33.2 199.5±31.3 A<B ** Triglyceride (mg/dl) 105.5±59.6 153.7±80.2 176.1±76.2 A<B, C *** Glucose (mg/dl) 90.0±16.4 97.9±21.1 107.5±30.2 A<B, C *** HbA1c (%) 5.6±0.6 5.8±0.7 6.4±1.3 A<B<C *** Insulin (μu/ml) 4.0±2.0 6.7±3.1 8.4±3.4 A<B<C *** hs-crp (mg/dl) 0.13±0.28 0.17±0.31 0.45±0.85 A, B<C *** Values are Mean ± SD. ***, P<0.001; **, P<0.01. Abbreviation: BP, blood pressure; HDL, high density lipoprotein; LDL, low density lipoprotein; HbA1c, hemoglobin A1c; hs-crp, high sensitivity C-reactive protein. A, Normal; B, Overweight; C, Obesity
자료분석및처리이연구에서얻어진모든자료는윈도우용 11.0 SPSS 통계프로그램을이용하여기술통계치 (Mean ± SD) 를산출하였다. 허리둘레의정도에따른집단간차이를검증하기위해 independent sample t-test를실시하였으며, 체질량지수정도에따른정상, 과체중, 비만군의집단간차이를검증하기위해일원변량분석 (One-way ANOVA) 을실시하였다. 또한집단간유의한차이가있을경우 Bonferroni 방법을적용하여사후검증을실시하였다. 복부비만및체질량지수와심장의구조및기능과의관련성을알아보기위해 Pearson의상관분석을실시하였으며, 유의수준은 P<0.05로하였다. 결과대상자의생리학적특성 Table 1에서보는바와같이, 허리둘레에의해비만을분류한결과체중, 체질량지수, 근육량, 체지방률, 수축기및이완기혈압, LDL 콜레스테롤, 총콜레스테롤, 중성지방, 공복혈당, 당화혈색소, 인슐린은정상군에비해비만군에서유의하게높게나타났으며, HDL 콜레스테롤은낮게나타났다. 또한 Table 2에서보는바와같이, 체질량지수에의해비만을분류한결과체중, 허리둘레, 근육량, 체지방률, 수축기및이완기혈압, 중성지방, 공복혈당, 당화혈색소, 인슐린, hs-crp는정상군에서과체중군, 비만군으로진행할수록점진적으로유의하게높게나타났으며, HDL 콜레스테롤은점진적으로낮게나타났다. 또한 LDL 콜레스테롤과총콜레스테롤은정상군에비해과체중군에서유의하게높게나타났다. 허리둘레에따른심장구조와기능의차이 Table 3에서보는바와같이, 허리둘레로비만을분류하여심장구조에차이를검증한결과정상군에비해비만군에서좌심실이완기중격두께 (P=0.002) 와수축기중격두께 (P<0.001) 가유의하게두꺼운것으로나타났다. 또한비만군의좌심실이완기말직경과좌심실이완기말용적역시정상군보다각각유의하게두껍고컸다 (P= 0.008, P=0.001). 좌심실이완기와수축기후벽두께도비만군이두꺼웠고 ( 각각 P<0.001, P<0.001), 좌심실질량역시비만군이유의하게컸다 (P<0.001). 허리둘레로비만을분류하여심장기능의차이를검증 Table 3. Cardiac structure and function on the basis of waist circumference Cardiac structure Variables Normal Obese IVSd (mm) 8.9±1.2 9.3±1.5 ** IVSs (mm) 13.8±1.9 14.6±2.1 *** LVEDD (mm) 47.0±3.9 48.3±5.4 ** LVESD (mm) 28.5±3.5 29.1±5.0 LVEDV (ml) 103.1±21.4 111.3±25.0 ** LVESV (ml) 31.7±10.0 34.1±16.6 LVPWd (mm) 8.6±1.2 9.4±2.3 *** LVPWs (mm) 14.4±2.1 15.2±2.0 *** LV mass (g) 173.3±42.4 197.6±49.7 *** LV mass index (g/m 2 100.6±26.3 100.6±26.3 ) Cardiac EF (%) 69.8±6.0 70.3±9.1 systolic function FS (%) 39.5±5.1 40.9±6.5 DT (m/sec) 195.5±55.2 187.0±58.5 Cardiac diastolic function E (cm/sec) 69.3±15.7 68.6±15.2 A (cm/sec) 50.4±13.7 57.0±13.9 *** E/A ratio (%) 1.47±0.53 1.26±0.38 *** E' (cm/sec) 13.3±6.7 11.8±2.7 *** E/E' ratio (%) 5.4±1.3 6.0±1.6 *** Values are Mean ± SD. ***, P<0.001; **, P<0.01. Abbreviation: IVSd, interventricular septal thickness at diastole; IVSs, interventricular septal thickness at systole; LVEDD, left ventricular end diastolic diameter; LVESD, left ventricular end systolic diameter; LVEDV, left ventricular end diastolic volume; LVESV, left ventricular end systolic volume; LVPWd, left ventricular posterior wall diastole thickness; LVPWs, left ventricular posterior wall systole thickness; EF, ejection fraction; FS, fractional shortening; DT, deceleration time; E, mitral peak velocity of early filling; A, mitral peak velocity of late filling; E', early diastolic mitral annular velocity. 한결과정상군에비해비만군에서이완기심장기능을나타내는후기승모판혈류속도 (A-velocity) 가유의하게빠른것으로나타났으며 (P<0.001), E/A 비율은낮은것으로나타났다 P<0.001). 또한초기승모판륜혈류속도 (E'-velocity) 는비만군이유의하게느린것으로나타났으며 (P<0.001), E/E' 비율은유의하게높은것으로나타났다 (P<0.001). 체질량지수에따른심장구조와기능의차이 Table 4에서보는바와같이, 체질량지수로비만을분류하여심장구조에차이를검증한결과좌심실이완기중격두께와수축기중격두께모두정상군과과체중군에비해비만군에서두꺼운것으로나타났다 ( 각각 P<0.001). 또한좌심실이완기말직경과및용적은정상군에비해 - 144 -
Cardiac structure Cardiac systolic function Cardiac diastolic function Table 4. Cardiac structure and function on the basis of BMI Variables Mean ± SD SS MS Bonferroni IVSd (mm) 9.0±1.3 119.027 59.513 A, B<C *** IVSs (mm) 14.0±1.9 289.327 144.664 A, B<C *** LVEDD (mm) 47.3±4.3 545.550 272.775 A<B<C *** LVESD (mm) 28.6±3.9 39.996 19.998 NS LVEDV (ml) 104.7±22.4 13450.107 6725.053 A<B<C *** LVESV (ml) 32.2±11.6 413.620 206.810 NS LVPWd (mm) 8.7±1.5 92.798 46.399 A, B<C *** LVPWs (mm) 14.5±2.1 245.814 122.907 A, B<C *** LV mass (g) 178.1±44.9 182213.6 91106.788 A<B<C *** LV mass index (g/m 2 ) 100.9±25.5 5896.030 2948.015 A<B * EF (%) 69.9±6.7 289.220 144.610 A<B * FS (%) 39.8±5.4 147.574 73.787 NS DT (m/sec) 193.8±55.9 3099.494 1549.747 NS E (cm/sec) 69.1±15.6 2072.826 1036.413 A>B * A (cm/sec) 51.7±14.0 5307.023 2653.511 A, B<C *** E/A ratio (%) 1.43±0.51 6.695 3.348 A>B *** E' (cm/sec) 13.0±2.7 403.434 201.717 A, B>C *** E/E' ratio (%) 5.5±1.4 50.963 25.482 A<B<C *** ***, P<0.001; * : P<0.05; NS, not significant. A, Normal; B, Overweight; C, Obesity 과체중군이두꺼운것으로나타났으며 ( 각각 P<0.001, P<0.001), 과체중군에비해비만군이두꺼운것으로나타났다. 좌심실이완기와수축기후벽두께는정상군과과체중군에비해비만군에서두꺼운것으로나타났다 ( 각각 P<0.001, P<0.001). 좌심실질량은정상군에비해과체중군이큰것으로나타났으며 (P<0.001), 과체중군에비해비만군이큰것으로나타났다 (P<0.001). 또한좌심실질량지수역시정상군에비해과체중군에서유의하게큰것으로나타났다. 체질량지수로비만을분류하여심장기능의차이를검증한결과수축기심장기능을나타내는구혈률은정상군에비해과체중군에서높게나타났다. 또한이완기심장기능을나타내는초기승모판혈류속도 (E-velocity) 는정상군에비해과체중군에서의미있게느렸고 (P=0.014), 후기승모판혈류속도 (A-velocity) 는정상군과과체중군에비해비만군에서빨랐다 (P<.001). E/A 비율은정상군이과체중군에비해높은것으로나타났다 (P<0.001). 초기승모판륜속도 (E'-velocity) 는비만군에비해정상군과과체중군이빨랐다. E/E' 비율은정상군에비해과체중군이높게나타났으며, 과체중군에비해비만군에서높게나타났다 (P<0.001). 허리둘레, 체질량지수와심장구조및기능의관련성 Table 5에서보는바와같이비만을평가하는허리둘레, 체질량지수와심장구조및기능과의상관성을검증한결과허리둘레와체질량지수모두심장기능과정의상관성 (positive correlation) 이있는것으로나타났으며, 그중좌심실질량은허리둘레, 체질량지수와유의한정의상관성을보였다 (P<0.05). 허리둘레, 체질량지수와수축기심장기능과의관련성을검증한결과체질량지수는구혈률및좌심실내경단축률과유의한상관성을보이는것으로나타났으며, 허리둘레는좌심실내경단축률과유의한정의상관성을보였다. 허리둘레, 체질량지수와이완기심장기능과의관련성을검증한결과초기승모판혈류속도 (E-velocity), E/A 비율, 초기승모판륜혈류속도 (E'-velocity) 는유의한부의상관성 (negative correlation) 을보이는반면, 후기승모판혈류속도 (A-velocity) 와는유의한정의상관성을보이는것으로나타났다. 또한체질량지수는 E/E' 비율과유의한정의상관성을보이는것으로나타났다. - 145 -
Table 5. Pearson's correlation coefficients of BMI and waist circumference Cardiac structure Variables BMI Waist circumference IVSd (mm).458 **.471 ** IVSs (mm).489 **.543 ** LVEDD (mm).292 **.305 ** LVESD (mm).123 **.168 ** LVEDV (ml).287 **.318 ** LVESV (ml).119 **.162 ** LVPWd (mm).385 **.456 ** LVPWs (mm).422 **.447 ** LV mass (g).520 **.542 ** LV mass index (g/m 2 ).188 **.190 ** Cardiac systolic EF (%).093 *.054 function FS (%).107 *.105 * Cardiac diastolic function **, P<0.01; *, P<0.05. DT (m/sec).006.035 E (cm/sec) -.153 ** -.261 ** A (cm/sec).233 **.143 ** E/A ratio (%) -.269 ** -.301 ** E' (cm/sec) -.381 ** -.372 ** E/E' ratio (%).203 **.082 고 우리나라에서과체중과비만인구는서구화된생활양식으로인해급속한증가를보이고있다. 비만은당뇨병, 고혈압, 이상지질혈증및심혈관질환의발병과관련성을보이고있으며 (Massie, 2002), 죽상경화증의결과가아닌비만그자체로도직접적인심장구조와기능에변화를초래한다고보고되고있다 (Sung & Kim, 2010). 정상인과비교해비만인의경우좌심실이완기말직경, 좌심실벽두께및좌심실질량이증가한다 (Alpert et al., 1985; Ryu et al., 2008). 이연구에서건강한성인을대상으로허리둘레에따른심장구조의차이를분석한결과정상군에비해비만군에서좌심실이완기와수축기중격두께, 좌심실이완기와수축기후벽두께가두꺼운것으로나타났으며, 좌심실이완기말직경, 좌심실이완기말용적, 좌심실질량은비만군에서더큰것을확인할수있었다. 이와같이비만은좌심실비대의독립적인요인이며, 과도한지방대사활성으로인해심박출량및총혈액용적의증가와같은혈역학적인변화를일으킨다 (Sung & 찰 Kim, 2010). 이러한메카니즘을통해비만은좌심실비대와좌심실벽스트레스를증가시키며, 이에대한보상작용으로편심성좌심실비대 (eccentric left ventricular hypertrophy) 를초래한다 (Wong et al., 2004; Avelar et al., 2007). 그러나최근의연구들에서구심성좌심실비대 (concentric left ventricular hypertrophy) 가비만인에서우세하게나타난다고보고되고있다 (Iacobellis et al., 2004a; Peterson et al., 2004b). 이연구에서는비만군에서중격과후벽두께의증가뿐아니라좌심실이완기말직경도크게나타나편심성과구심성심장비대가복합적으로나타나는것을확인할수있었다. 그외에도비만은심외막의지방량과심근내의지방침윤증가를야기시켜좌심실질량을증가시키며, 비만인에서교감신경활성화는후부하 (afterload) 증가및심장수축력증가로인한구심성좌심실비대를유발한다 (Iacobellis et al., 2004b). 허리둘레에따른심장기능의차이를분석한결과는정상군에비해비만군에서심장의이완기기능을나타내는후기승모판혈류속도 (A-velocity) 는빠른것으로나타났으며, E/A 비율은낮은것으로나타났다. 또한초기승모판륜혈류속도 (E'-velocity) 는비만군에서느린것으로나타났으며, E/E' 비율은높은것으로나타났다. 그러나좌심실수축기기능은집단간차이가없는것으로나타났다. 이러한결과는비만인의경우정상인에비해 E/A 비율은낮고, 좌심실충만압을나타내는 E/E' 비율이높아진다고보고한선행연구들과일치하는결과이며 (Sharpe et al., 2006; Libhaber et al., 2009), 비만인에서 E/A 비율의감소는주로후기승모판혈류속도 (A-velocity) 의증가와상대적으로변화가없는초기승모판혈류속도 (E-velocity) 때문이다 (Chadha et al., 2009). 비만에따른좌심실수축기기능은정상또는증가한다고보고되고있다 (Wong et al., 2004; Avelar et al., 2007). 그러나좌심실이완기기능장애는수축기기능장애가나타나기전에나타나는데, 그원인으로는혈역학적인변화로인한좌심실비대와그로인한이완기기능장애가동반되기때문이라고보고되고있다 (Chakko et al., 1991). 또한비만과관련된호르몬과사이토카인의방출, 심근의콜라겐축적, 심장대사의변화, 미토콘드리아의기능장애, 산화적스트레스등이비만인에서심장기능이감소하는원인으로알려져있다 (Sung & Kim, 2010). 이연구에서는임상에서널리사용되는체질량지수에 - 146 -
따라정상군, 과체중군, 비만군의세군으로분류하여심장구조및기능의차이를분석한결과심장의구조를나타내는좌심실이완기말직경과좌심실이완기말용적, 좌심실질량은비만의단계에따라큰것으로나타났다. 심장의이완기기능을나타내는초기승모판혈류속도 (E-velocity) 는정상군에비해과체중군에서느린것으로나타났으며, E/A 비율은정상군이과체중군에비해높은것으로나타났다. 또한 E/E' 비율은비만의단계에따라높게나타났다. 이와같은결과는비만단계에따라좌심실재형성, 좌심실이완기충만압의상승과관련이있으며, 이완기기능의지표들이정상에서과체중으로진행하면서현저하게차이를보이고있다는과거의연구결과와일치한다 (Powell et al., 2006; Ryu et al., 2008). 앞서제시한허리둘레의결과와같이체질량지수에의한비만기준역시심장구조와기능에차이를보이고있으며, 비만군으로진행하기전단계인과체중군에서조기에심장의구조적, 기능적차이를보이고있어과체중및비만환자에서좌심실기능의조기변화를보고한연구와일치하는결과이다 (Ryu et al., 2008). 또한체중저하는좌심실의이완기및수축기기능과좌심실질량의향상을가져온다고보고하고있으며 (Alaud-din et al., 1990, Hinderliter et al., 2002; de las Fuentes et al., 2009), 이러한결과를통해비만으로진행하기전단계군인과체중군도비만군으로간주하여규칙적운동을통한체중개선이이루어져야할것으로사료된다. 체질량지수는좌심실질량, 좌심실벽두께, 좌심실이완기말직경과관련이있으며, 비만은만성적혈액용량부하에의한심장적응의초기단계인이완기기능장애와관련이있다 (Ryu et al., 2008). 이연구에서도허리둘레, 체질량지수와심장구조및기능의상관성을검증한결과허리둘레와체질량지수모두심장구조와이완기기능간에상관성이있는것으로나타났다. 특히심장구조중좌심실질량과가장상관성이높은것으로나타났다. 그러나비만한고혈압환자를대상으로체질량지수에의한비만보다복부비만이좌심실이완기기능과더밀접한관련이있다는결과 (Kim et al., 2006) 와는다소차이를보이고있으며, 이러한결과의차이는여타질환이없는비만인만을대상으로한본연구와대상자가다르기때문으로사료된다. 이연구의제한점으로는체질량지수와허리둘레에의한비만분류방법이상관관계에상호영향을미칠수있 을것으로판단된다. 추후독립적으로각각의비만요인이높은군으로분류한연구가필요할것으로생각된다. 결론적으로심장의구조와기능은인체측정학적변인인체질량지수및허리둘레와관련이있으며, 체질량지수및허리둘레기준에의한비만은심장의구조적변화뿐아니라기능적인변화를유도하는것으로나타났다. REFERENCES Aasum E, Hafstad AD, Severson DL, Larsen TS. Age-dependent changes in metabolism, contractile function, and ischemic sensitivity in hearts from db/db mice. Diabetes 2003. 52: 434-441. Alaud-din A, Meterissian S, Lisbona R, MacLean LD, Forse RA. Assessment of cardiac function in patients who were morbidly obese. Surgery 1990. 108: 809-818. Alpert MA, Terry BE, Kelly DL. Effect of weight loss on cardiac chamber size, wall thickness and left ventricular function in morbid obesity. Am J Cardiol. 1985. 55: 783-786. Arkin JM, Alsdorf R, Bigornia S, Palmisano J, Beal R, Istfan N, Hess D, Apovian CM, Gokce N. Relation of cumulative weight burden to vascular endothelial dysfunction in obesity. Am J Cardiol. 2008. 101: 98-101. Avelar ET, Cloward V, Walker JM, Farney RJ, Strong M, Pendleton RC, Segerson N, Adams TD, Gress RE, Hunt SC, Litwin SE. Left ventricular hypertrophy in severe obesity: interactions among blood pressure, nocturnal hypoxemia, and body mass. Hypertension 2007. 49: 34-39. Chadha DS, Gupta N, Goel K, Pandey RM, Kondal D, Ganjoo RK, Misra A. Impact of obesity on the left ventricular functions and morphology of healthy Asian Indians. Metab Syndr Relat Disord. 2009. 7: 151-158. Chakko S, Mayor M, Allison MD, Kessler KM, Materson BJ, Myerburg RJ. Abnormal left ventricular diastolic filling in eccentric left ventricular hypertrophy of obesity. Am J Cardiol. 1991. 68: 95-98. de las Fuentes LA, Waggoner D, Brown AL, Dávila-Román VG. Plasma triglyceride level is an independent predictor of altered left ventricular relaxation. J Am Soc Echocardiogr. 2005. 18: 1285-1291. de las Fuentes LA, Waggoner D, Mohammed BS, Stein RI, Miller BV 3rd, Foster GD, Wyatt HR, Klein S, Davila-Roman VG. Effect of moderate diet-induced weight loss and weight regain on cardiovascular structure and function. J Am Coll - 147 -
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