b -Thiazide diuretics : e.g. hydrochlorothiazide and Chlorthalidone have mild diuretic effect, but act synergistically when combined with loop diuretics. Not effective in renal impairment. Metolazone is a powerful thiazide & is combined with loop diuretics in severe and resistant HF.
* Loop & thiazide diuretics have no proven survival benefit. They give symptomatic relieve
c - Potassium sparing diuretics : Care with ACE-I & avoided in renal impairment . Spironolactone reduces mortality in doses of up to 25 mg when added to conventional therapy in moderate to severe HF. Risk of hyperkalaemia is high with doses of > 50 mg..
Ameloride & triamterene are weak but useful when combined with loop diuretics..
- reduce after load & pre load - reduce circulating levels of catecholamines, - reduce BP - reduce cardiac dilatation & CCF after extensive MI - improve exercise tolerance & survival in pts. with severe HF.
b- ARBs have similar effects to ACE-I but do not affect bradykinin metabolism.
c- Alpha blockers (prazocin) & direct smooth muscle relaxants (hydralazine) are not very effective in HF. CCBs reduce after load but have no prognostic benefit in HF. Diltiazem and verapamil are CI in HF.
d- Nitrates (glyceride trinitrates and isosorbide mononitrates) reduce preload and reduce pulm edema.Only
combination with hydralazine have proven prognostic value.
3- BB used in pts. with chronic stable HF (e.g. metoprolol, bisoprolol, atenolol and carvedilol), improve symptoms, exercise tolerance, LV function and mortality in pts. with HF. Initial doses should be low.
Digoxin : - cardiac glycoside, It blocks AV node and increases myocardial contractility. - used in severe HF with conventional therapy, AF, atrial flutter & SVT. - 90% is excreted unchanged in urine and accumulation can occur in renal failure. Digitoxin is used In renal failure. - Usual dose is 0.125-0.25 mg/d. with dose of 1mg in emergency
- SE of Digoxin include: HA, fatigue, muscle weakness, abd. Pain, N, V, Wt. loss & gynaecomastia.
- Digoxin toxicity include: anorexia, N, V, coloured vision with halo around objects (xanopsia), arrhythmias & fits. - TR of digoxin toxicity : By stopping the drug, restoration of ser. K and management of arrhythmias. Digoxin abs. in life threatening toxicity.
Adr., dobutamine, dopexopamine & dopamine are IV adrenergic agonist. They increase CO & improve perfusion but increase myocardial O2 requirements & aggravate cardiac ischemia. Volume depletion should be corrected before their use. Main use in pts. with acute LVF, following cardiac surgery & in pts. with end stage HF as a bridge to transplantation.
Dobutamine is a B2 agonist increasing cardiac contraction & has vasodil. effect by alpha blocker effect. Dose 2.5-10 mcg/kg/minute .
- Aminophylline 5 mg/kg IV ( 250-500) slowly to avoid the risk of precipitating ventricular arrhythmias. It is bronchodilator., vasodilt. & increases cardiac contractility. Usually used when bronchospasm is present.
- Monitor rhythm, O2 saturation.
- Venesection & mechanical methods of reducing venous return are ineffective and rarely used.