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Cac thuoc chong loan nhip tim

Cac thuoc chong loan nhip hien dang duoc su dung con co nhieu han che do hieu qua khong thuc su cao va co nhieu doc tinh.

 Hinh anh tim theo mat cat doc.
Trong hau het cac nghien cuu voi thuoc chong loan nhip ve ty le tu vong, nguoi ta chua dua ra duoc loi ich mot cach ro rang. Mat khac gioi han giua lieu co hieu qua dieu tri va lieu doc cua thuoc tuong doi hep. Vi vay nguoi thay thuoc buoc phai hieu ro duoc ly lam sang, lieu dung va cac tac dung bat loi cua cac thuoc chong loan nhip.

Cac thuoc chong loan nhip duoc phan loai dua tren cac co che tac dong vao giai doan dien sinh ly cua te bao tim (pha 0, 1, 2, 3, 4) ma Vaughan Williams dua ra (tu nam 1971 sau do duoc Singh, Hauswirth va Harrison bo sung them).

Cac thuoc chong loan nhip nam trong nhom I co tac dong lam cham dan truyen trong that do chen kenh Na+ vao nhanh tren mang te bao, duoc chia ra 3 nhom phu.

- Nhom IA co tac dong lam giam tinh dan truyen cua cac te bao tren he dan truyen, keo dai thoi ky tro va khoang QT. Cac thuoc nhom nay cung lam giam suc co bop co tim, bao gom: quinidin, procainamide, disopiramide, moricizine.

- Nhom IB co tac dong gan tuong tu nhu IA nhung it hon doi voi tinh dan truyen; lam ngan thoi ky tro co hieu luc nhat la dien the hoat dong te bao, giup cho thoi ky tro cua cac to chuc dong deu hon. Cac thuoc nay it anh huong toi tinh co bop cua co tim, bao gom: lidocain, tocainide, mexiletin.

- Nhom IC co tac dong lam cham toc do dan truyen tren hau het cac to chuc tim (do tac dung keo dai thoi ky tro co hieu luc) gay keo dai khoang PR, QRS, trong khi co chut it hieu luc tren giai doan tai cuc va khoang QT. Cac thuoc nhom nay cung lam giam nhe suc co bop co tim, bao gom: flecainide, encainide, propafenone.

Cac thuoc chong loan nhip nam trong nhom II co tac dong uc che thu the giao cam b. Cac thuoc nay thuong co hieu luc voi cac loan nhip va con nhip nhanh tren that thu phat do tang hoat hoa giao cam qua muc, nhung lai khong co hieu luc trong dieu tri loan nhip nang nhu con nhanh that man tinh. Cac thuoc trong nhom nay lam giam dang ke suc co bop co tim do vay phai het suc luu y cac chong chi dinh, gom: propranolon, esmolol, acebutolol...

Cac thuoc chong loan nhip nam trong nhom III co tac dong uu the keo dai thoi gian dien the hoat dong va thoi ky tro cua tim, bao gom: amiodarone, bretylium, sotalol, ibutilide trong do thuoc hay duoc su dung nhat la amiodarone (biet duoc cordarone).

Cac thuoc chong loan nhip nam trong nhom IV co tac dong uc che kenh Ca++, bao gom: verapamil, ditiazem. Cac thuoc thuoc nhom chen kenh calci gom rat nhieu, tuy nhien tac dung chong loan nhip thi chi co 2 thuoc la verapamil va diltiazem.

Ngoai ra con co mot so thuoc khac khong nam trong phan loai cua Vaughan Williams duoc dung trong dieu tri roi loan nhip tim nhu digoxin, adenosine (biet duoc ATP; stryadine), atropin...

Do su han che cua bang phan loai cac thuoc chong loan nhip cua Vaughan Williams, ngay nay nguoi ta phan loai dua tren co so hieu luc khac nhau cua thuoc chong loan nhip tren cac kenh ion, cac thu the va cac bom qua mang te bao. Nhu vay nhom thuoc chong loan nhip se duoc chia theo tac dong cua thuoc truoc tien chu yeu “troi”, thu den la tac dong “lien quan” co the xuat hien tren lam sang. Cach phan loai nhu vay co the thoa man voi ca mot so thuoc khac co tac dung tren nhip ma da khong co trong bang phan loai cua Vaughan Williams.

Nhu vay theo he thong phan loai moi, vi du: quinidine la thuoc doi khang kenh Na (giam nhe thoi gian co dinh doi voi giai doan hoi phuc) voi hoat dong uc che kenh K va thu the a. Dieu nay mo ta hoan chinh hon va chinh xac tac dong duoc ly cua thuoc. Khi ket hop cac tac dong tren dien sinh ly cua thuoc nay chung ta co the tien doan duoc hieu luc giong nhu no xuat hien tren co the song. Trong truong hop nay quinidin se co 3 tac dong mong doi: lam cham dan truyen, keo dai thoi ky tro co hieu qua va gian mach.

Cac thuoc chong loan nhip deu co tac dung gay loan nhip. Nguoi ta chia ra 2 nhom: nhom gay loan nhip chen cac kenh Na+ va nhom gay loan nhip “xoan dinh” (torsades de Pointes).

- Nhom gay loan nhip chen cac kenh Na+: cac thuoc trong nhom I doi khi co tac dung khong du tinh truoc duoc do gay gian rong phuc bo QRS tren dien tim. Tang mot cach nghich dao tan so hoac khoang thoi gian cua nhip nhanh that hoac cuong that. Lam giam nghen nhi that trong cuong nhi toi 1:1 gay tang tan so that toi 200-250 lan/phut. Tang nguong cua may tao nhip hoac chong rung.

- Nhom gay loan nhip xoan dinh: day duoc coi nhu mot tac dung phu pho bien cua mot so thuoc chong loan nhip nam trong nhom IA va III do keo dai khoang QT. Cac yeu to nguy co them vao de dan den loan nhip nay la: gioi nam, roi loan chuc nang that trai, nhip cham va roi loan dien giai dac biet la kali mau thap va magie mau thap. Vi vay can xem xet benh nhan ky luong, dac biet la xet nghiem dien giai truoc khi dieu tri de de phong xoan dinh. Muc kali mau phai tren 4 mEq/L, dong thoi phai theo doi khoang QT tren dien tim truoc hoac sau khi cho thuoc hoac tang lieu. Khi xuat hien xoan dinh, ngay lap tuc tiem tinh mach cham magie sulphat (2g trong 10-20 phut) va du tinh kich thich tim (may tao nhip hoac truyen tinh mach lsoproterenol). Sau do can tiep tuc dieu chinh dien giai, nhat la kali, neu can thiet thi ngung hoac giam lieu thuoc gay keo dai QT. Tren lam sang can thiet phan biet giua xoan dinh voi nhanh that da dang xuat phat tu khoang QT binh thuong, boi vi sau do chung ta phai dieu tri bang thuoc nhom I nhu lidocaine va co the tro nen xau di boi dieu tri khong dung doi voi xoan dinh.

Viec nam vung tac dung, lieu dung, hap thu, chuyen hoa, thai tru, tuong tac va chi dinh dieu tri cua thuoc, chong loan nhip trong tung truong hop la het suc can thiet. Mat khac khi co dau hieu ngo doc hoac tac dung khong mong muon cua thuoc, nguoi thay thuoc cung can phai nam duoc de xu tri kip thoi.

TS. Nguyen Duc Hai