龐勝峰(綜述),何勝虎(審校)
(1.興化市戴南人民醫(yī)院心內(nèi)科,江蘇泰州 225700;2.蘇北人民醫(yī)院心內(nèi)科,江蘇揚(yáng)州 225000)
高血壓是心腦血管疾病的重要危險(xiǎn)因素,我國高血壓患者約占全球高血壓總?cè)藬?shù)的1/5,18歲以上的成人高血壓患病率為18.8%[1]。研究表明,心臟自主神經(jīng)功能紊亂在原發(fā)性高血壓的發(fā)病過程中起重要作用[2]。Montano等[3]的研究提示,交感神經(jīng)張力過高可能參與高血壓發(fā)病的始動(dòng)機(jī)制。心率變異性(heart rate variability,HRV)作為反映自主神經(jīng)系統(tǒng)對心臟和血管調(diào)節(jié)動(dòng)態(tài)平衡的無創(chuàng)性指標(biāo),對評價(jià)心血管疾病進(jìn)程中自主神經(jīng)功能具有重要的臨床價(jià)值[4],可以作為預(yù)測某些心臟疾病嚴(yán)重程度和預(yù)后的指標(biāo)之一[5]。通過對自主神經(jīng)功能紊亂與HRV的研究,對指導(dǎo)原發(fā)性高血壓的診斷、治療及預(yù)后判斷有一定的實(shí)用價(jià)值[6]。現(xiàn)就原發(fā)性高血壓HRV的研究進(jìn)展予以綜述。
HRV是指逐次心動(dòng)周期之間的時(shí)間變異性。正常竇性心律之間不會(huì)絕對整齊,存在微小的漲落,通過心電圖中R-R間期的測量,獲得的時(shí)間變異性即為HRV。HRV能反映自主神經(jīng)系統(tǒng)交感與副交感神經(jīng)的活性及其平衡協(xié)調(diào)功能,正常生理狀態(tài)下心臟的規(guī)律活動(dòng)靠交感與副交感神經(jīng)的相互作用維持,這種作用一旦失去平衡將會(huì)導(dǎo)致心血管系統(tǒng)功能紊亂,HRV能檢測到自主神經(jīng)功能早期的異常變化,可能具有早期診斷和預(yù)測價(jià)值[7]。
HRV的分析方法有線性分析和非線性分析,前者包括時(shí)域分析和頻域分析,后者包括散點(diǎn)圖、關(guān)聯(lián)維數(shù)、李雅普諾夫指數(shù)、復(fù)雜度等。臨床上非線性分析法使用較少,還處于探索階段,時(shí)域分析法和頻域分析法使用較廣泛[8]。
2.1 時(shí)域分析 時(shí)域分析常用的指標(biāo)有:①總體標(biāo)準(zhǔn)差(SDNN),即指24 h內(nèi)所有的竇性心搏R-R間期的標(biāo)準(zhǔn)差,主要反映交感神經(jīng)和副交感神經(jīng)總的活性,評價(jià)心臟自主神經(jīng)系統(tǒng)對心血管功能的整體調(diào)節(jié),正常參考值為(141±39)ms;②均值標(biāo)準(zhǔn)差 (SDANN),指全程24 h測量得到的所有連續(xù)5 min R-R間期平均值的標(biāo)準(zhǔn)差,是評價(jià)HRV長周期的指標(biāo),主要反映交感神經(jīng)活性,正常參考值為(127±35)ms;③差值均方的平方根(rMSSD),指相鄰R-R間期差值的均方根,是評價(jià)HRV短周期的指標(biāo),反映心臟副交感神經(jīng)的張力,正常參考值為(27±12)ms;④每5分鐘竇性R-R間期標(biāo)準(zhǔn)差的平方根 (SDNNi),描述分鐘內(nèi)HRV的大小,反映交感神經(jīng)張力的變化;⑤相鄰R-R間期相差≥50 ms占總竇性心搏的百分?jǐn)?shù)(PNN50),是反映副交感神經(jīng)張力的敏感指標(biāo),正常值為 10%[9]。
2.2 頻域分析 頻域分析常用的指標(biāo)有:①高頻功率,只受迷走神經(jīng)介導(dǎo),反映迷走神經(jīng)張力,受呼吸影響較大,正常值為(975±203)ms2;②低頻功率,反映交感神經(jīng)和副交感神經(jīng)的共同作用,主要反映交感神經(jīng)功能,正常值為(1170±416)ms2;③極低頻功率,反映交感神經(jīng)活動(dòng)的指標(biāo);④總功率,參考值為(3466±1018)ms2;⑤低高頻比值(低頻功率/高頻功率),反映交感神經(jīng)和副交感神經(jīng)之間的動(dòng)態(tài)平衡,正常范圍 1.5 ~2.0[9]。
高血壓的發(fā)病機(jī)制目前仍沒有完全明確,研究表明,高血壓患者血漿腎上腺素能神經(jīng)遞質(zhì)水平比同齡正常血壓者高25%~30%[10],說明存在交感神經(jīng)活性過度激活。另有研究表明,高血壓患者HRV與血壓水平相關(guān),隨著血壓分級的上升,自主神經(jīng)功能損害逐漸加重,高血壓患者病死率升高,預(yù)后下降[11]。觀察高血壓患者HRV的變化,不但有利于維持血壓本身的穩(wěn)定,還能早期發(fā)現(xiàn)心臟自主神經(jīng)功能的損害,有利于早期發(fā)現(xiàn)靶器官的損害,及時(shí)干預(yù)可延遲高血壓并發(fā)癥的發(fā)生。
3.1 正常血壓高值者HRV的變化 Pal等[12]分析了32例血壓正常者,28例正常血壓高值者和31例高血壓者的HRV指標(biāo)發(fā)現(xiàn),正常血壓高值者交感神經(jīng)活性增加,迷走神經(jīng)活性抑制,心臟自主神經(jīng)功能受損。有研究證實(shí),正常血壓高值者HRV指標(biāo)SDNN、低頻功率、高頻功率相對正常血壓者已下降[13]。Dogru等[14]通過對294例正常血壓患者HRV的研究發(fā)現(xiàn),正常血壓高值的對象出現(xiàn)交感神經(jīng)活性增加和副交感神經(jīng)神經(jīng)活性降低,正常血壓高值者HRV降低后發(fā)生高血壓的概率增加。
3.2 非杓型高血壓與HRV 研究發(fā)現(xiàn),高血壓非杓型組HRV指標(biāo)低于杓型組,說明血壓晝夜節(jié)律異常者心臟自主神經(jīng)功能損害較重[15-16]。高血壓晨峰現(xiàn)象引起SDANN、rMSSD及PNN50水平下降,導(dǎo)致心臟迷走神經(jīng)功能損害,心律失常風(fēng)險(xiǎn)增加[17]。梁凌等[18]觀察了342例老年高血壓患者,發(fā)現(xiàn)HRV時(shí)域指標(biāo)下降與晨峰現(xiàn)象有關(guān),說明兩者之間存在聯(lián)系,表現(xiàn)為交感神經(jīng)活性增加、副交感神經(jīng)活性減弱,一旦副交感神經(jīng)活性下降到不能對抗交感神經(jīng)活性,則引起心室顫動(dòng)域降低,易誘發(fā)心室顫動(dòng),甚至發(fā)生猝死。
3.3 脈壓與HRV 脈壓為收縮壓減去舒張壓的差,脈壓越大,動(dòng)脈硬化越重,發(fā)生高血壓心室肥厚、冠狀動(dòng)脈粥樣硬化性心臟病、頸動(dòng)脈粥樣硬化的風(fēng)險(xiǎn)越大[19-21]。老年患者常表現(xiàn)為單純收縮期高血壓,同時(shí)因動(dòng)脈硬化,常出現(xiàn)寬脈壓,有研究證實(shí),老年高血壓患者血壓越高,自主神經(jīng)功能損害越嚴(yán)重,HRV明顯低于正常老年人[22]。
3.4 高血壓合并靶器官損害的HRV變化 高血壓患者易發(fā)生心、腎等靶器官損害,在治療高血壓的過程中及早發(fā)現(xiàn)靶器官損害并及時(shí)治療成為降低患者心血管并發(fā)癥和死亡的關(guān)鍵。Melillo等[23]觀察了200例高血壓患者HRV指標(biāo)與腎小球?yàn)V過率、頸動(dòng)脈內(nèi)膜中層厚度、左心室質(zhì)量的關(guān)系,發(fā)現(xiàn)靶器官損害與低頻功率/高頻功率下降相關(guān),監(jiān)測患者的HRV指標(biāo)對于患者靶器官的損害和防治具有重要意義。腎損害是高血壓的常見并發(fā)癥,最終引起腎衰竭,因此對腎損害的早期診斷和治療極其重要。Thomson等[24]研究表明,HRV與高血壓早期腎損害存在相關(guān)性。有研究證實(shí),終末期腎病與HRV下降相關(guān),經(jīng)過血液透析的患者高頻功率、SDNN增加,心臟自主神經(jīng)功能改善[25]。Chandra等[26]認(rèn)為,HRV 下降可能是高血壓腎損害患者發(fā)生心臟意外的危險(xiǎn)信號,通過分析其變化,可評估疾病的預(yù)后,指導(dǎo)臨床用藥。Singh等[27]研究發(fā)現(xiàn),慢性腎衰竭患者HRV在臨終心室纖顫發(fā)作前明顯下降。高血壓患者隨著腎功能的下降,HRV降低,自主神經(jīng)功能紊亂加重,增加心血管事件的發(fā)生。左心室肥厚是原發(fā)性高血壓患者最常見的靶器官損害,可能與性別、年齡、血壓升高程度、遺傳、神經(jīng)體液等因素相關(guān)。Alter等[28]研究了86例竇性心律的心臟肥大患者及91例健康對照的HRV時(shí)域指標(biāo),發(fā)現(xiàn)前者SDNN、SDNNi明顯低于后者,差異有統(tǒng)計(jì)學(xué)意義,說明左心室肥厚患者自主神經(jīng)功能受損。Makowski等[29]發(fā)現(xiàn),原發(fā)性高血壓不伴左心室肥厚組有相對優(yōu)勢的交感神經(jīng)活性存在,而原發(fā)性高血壓伴左心室肥厚則導(dǎo)致迷走神經(jīng)和副交感神經(jīng)活性逐漸抑制降低,HRV降低,表明HRV下降程度與高血壓左心室肥厚呈正相關(guān),觀察HRV的改變可以反映左心室受累程度。
4.1 二甲雙胍 二甲雙胍可通過調(diào)節(jié)血脂、降低血漿非酯化脂肪酸來改善HRV,Mouridsen等[30]觀察到,隨著體質(zhì)量下降,膽固醇降低,HRV指標(biāo)中SDNN增加9.2%、SDNNi增加11.4%、PNN50增加2.4%,心臟自主神經(jīng)功能改善。Manzella等[31]發(fā)現(xiàn),肥胖2型糖尿病患者服用二甲雙胍治療4個(gè)月后,患者HRV指標(biāo)中低頻功率和低頻功率/高頻功率降低、高頻功率升高,交感神經(jīng)活性也相應(yīng)降低。Apaijai等[32]使用二甲雙胍和維格列汀治療有胰島素抵抗的成年大鼠3周后發(fā)現(xiàn),兩者均可改善HRV,保護(hù)心臟。二甲雙胍還能通過抗氧化、抗炎作用,抑制白細(xì)胞介素1β、腫瘤壞死因子α的表達(dá)[33],減少炎性因子釋放,改善 HRV,恢復(fù)自主神經(jīng)功能[34]。另外,王國民等[35]認(rèn)為,二甲雙胍可以降低血壓,從而改善自主神經(jīng)功能。
4.2 β受體阻滯劑 1999年,Burger等[36]證實(shí),在穩(wěn)定型心絞痛患者中使用β受體阻滯劑后,HRV明顯改善。Guzzetti等[37]研究顯示,阿替洛爾在治療原發(fā)性高血壓中不僅增加高頻功率波動(dòng),而且使低頻功率振蕩減小,這種交感神經(jīng)活性降低同樣存在于心肌梗死后使用美托洛爾和心力衰竭使用醋丁洛爾的患者中。有研究證實(shí),高血壓患者使用比索洛爾治療1個(gè)月后,總功率顯著升高[38]。高血壓伴左心室肥厚的患者使用美托洛爾 20周后,SDNN、rMSSD、PNN50、高頻功率明顯升高[39]。Targoński等[40]觀察 52 例充血性心力衰竭患者晚間服用長效β受體阻滯劑后發(fā)現(xiàn),患者平均心率顯著降低,低頻功率/高頻功率的比值顯著降低,改善了充血性心力衰竭的自主神經(jīng)張力。β受體阻滯劑主要通過抑制腎上腺素能受體、減慢心率、降低血壓、減少兒茶酚胺對心臟的損害等多方面來恢復(fù)交感-副交感神經(jīng)在心血管疾病中的平衡。
4.3 血管緊張素轉(zhuǎn)換酶抑制劑及血管緊張素受體阻滯劑Menezes等[41]發(fā)現(xiàn),高血壓患者服用血管緊張素轉(zhuǎn)換酶抑制劑3個(gè)月后,HRV的SDNN、PNN50和低頻功率等恢復(fù)接近正常,副交感神經(jīng)張力恢復(fù),自主神經(jīng)功能失衡得到改善??赡艿臋C(jī)制為血管緊張素轉(zhuǎn)換酶抑制劑通過改善血流動(dòng)力學(xué),干擾交感神經(jīng)的傳入功能,增加迷走神經(jīng)對心臟的影響,提高HRV[42]。雷米普利改變了高血壓患者自主神經(jīng)系統(tǒng)平衡,使副交感神經(jīng)張力增加和交感神經(jīng)張力降低;另外,舒張壓減少與中間頻率HRV增加之間呈負(fù)相關(guān),這意味著雷米普利對壓力感受性反射復(fù)位有一定作用,且其改善HRV的效果優(yōu)于卡托普利[43]。另有研究發(fā)現(xiàn),高血壓患者使用氯沙坦治療4周后,SDNN、rMSSD明顯改善[38]。伴有左心室肥厚的患者予以氯沙坦聯(lián)合氫氯噻嗪治療20周后,HRV指標(biāo)中 SDNN、rMSSD、PNN50、高頻功率明顯升高,自主神經(jīng)功能得到改善[39]。
4.4 鈣離子拮抗劑 Kawano等[44]研究發(fā)現(xiàn),地爾硫艸卓可以抑制交感神經(jīng)張力,增加副交感神經(jīng)張力,改善HRV。對在靜息狀態(tài)下迷走神經(jīng)占優(yōu)勢的患者使用氨氯地平后,自主神經(jīng)調(diào)節(jié)功能亦可得到改善[45]。硝苯地平、維拉帕米、氟桂利嗪等鈣離子拮抗劑對HRV指標(biāo)的影響提示自主神經(jīng)功能的恢復(fù)可能與鈣離子拮抗劑激活某些神經(jīng)介質(zhì)有關(guān)[46]。
高血壓作為一種全身性疾病,存在交感神經(jīng)張力增高和副交感神經(jīng)張力下降。隨著血壓的升高自主神經(jīng)功能損害加重、病程的延長,心律失常、心臟性猝死、心肌梗死、腦血管意外及其他心血管突發(fā)事件發(fā)生的風(fēng)險(xiǎn)增加。在臨床工作中早期檢測到自主神經(jīng)功能損害并及時(shí)予以藥物干預(yù),可以降低心血管事件發(fā)生,改善患者預(yù)后。
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