In mitral stenosis the mitral orifice is narrowed by thickening of the valves or their adherence together so as to obstruct the filling of the ventricle from the auricle. The natural compensation in this case is secured through hypertrophy and dilatation of the left auricle and of the right ventricle, so that, by added pressure, the proper amount of blood is forced through the narrowed aperture. Under digitalis, on the one hand, the filling of the left ventricle through this narrowed orifice is favored by a lengthened diastole (and the strengthening of the left auricle and right ventricle), and this has a slight tendency to improve the systemic circulation. On the other hand, digitalis does not remove the stenosis; and there is always the possibility that while the obstruction to the exit of blood at the mitral orifice remains unchanged, any increased output from a right ventricle already dilated and hypertrophied may result merely in increased pulmonary engorgement. This shows in congestion at the bases of the lungs, transudation of fluid into the pleural cavity, edema of the lungs, or hemorrhage from the lungs.

So in mitral stenosis, when the auricle and ventricle are beating in normal rhythm, the systemic circulation gets but little help from digitalis, and the danger of congestion in the lungs is increased. But when there is auricular fibrillation - and auricular fibrillation is more common with mitral stenosis than with any other lesion of the heart - the beneficial effects of digitalis far overshadow any possible disadvantageous ones.

In aortic stenosis the aortic orifice is narrowed by thickening of the valves or their adherence together, so that the blood is impeded in its passage into the aorta. The result is that the systemic circulation and coronary circulation tend to be inadequate. In an attempt to force more blood through the narrowed orifice by an increased power of systole the left ventricle is dilated and hypertrophied. The value of digitalis would not be interfered with by such a lesion.

So much for the heart lesions. This very brief review of these more common ones will serve to indicate that great judgment must be employed in the use of digitalis in heart disease.

But it must not be forgotten that the indication for digitalis is failure or threatened failure of compensation, and not at all the mere presence of a valvular lesion. When there is poor compensation, whether there is a valvular lesion or not, digitalis may be the best drug that we can employ.

In aneurysm of the aorta, aortitis, or arteriosclerosis, there is no contraindication to digitalis, so with these lesions, as without them, its use would depend on the needs of the heart. In pneumonia and other acute infectious diseases digitalis may be most useful in preventing or checking auricular fibrillation.

Fig. 24.

Fig. 24. - Case with mitral stenosis and auricular fibrillation. V.S., ventricular systole; R.P., radial pulse. Digipuratum reduced the pulse to normal rate, abolished the "pulse deficit" in the radial pulse as compared with the number of ventricular beats, and increased the urinary flow, as shown above. At the same time there was a very rapid and marked disappearance of dyspnea, cyanosis, and venous engorgement. The auricle continued to fibrillate (author's case).

There is no condition of the kidneys, per se, which calls for digitalis. Any striking diuretic effect is obtained only in conditions of venous engorgement from cardiac failure.

Summary Of Therapeutics

1. The indication for digitalis is failure or threatened failure of compensation. 2. Its most striking effects are seen in auricular fibrillation and when there is venous engorgement. 3. The drug's efficiency is not to be estimated by its effects on arterial pressure. 4. The mere presence of a valvular lesion is not a reason for using digitalis. 5. The diuretic effect is entirely due to improved circulation, and may be evident even when the heart weakness has not yet resulted in obvious edema and dropsy.

The Digitalis Allies

So far as the circulation is concerned, the uses of these are the same as those of digitalis itself. For administration by mouth not one of them has any advantage over digitalis and its active principles. Convallaria is less certain, and strophanthus is prone to cause diarrhea, while both have a smaller margin of safety between their therapeutic and poisonous doses. The difference between digitalis and strophanthus in their action upon the arteries is not observed in therapeutics. Cushny states that the tincture of strophanthus when mixed with water deteriorates and becomes inert in a few days.

But for intravenous administration strophanthin and ouabain are the most suitable, and have been used with remarkable, and in some instances dramatic, effects. So much as 1/65 grain (1 mg.) should never be employed intravenously at one dose if the patient has just previously been taking any of the drugs of the class by mouth. But it may be employed thirty-six hours after the last dose of strophanthus by mouth, or one week after the last dose of digitalis. If there is any doubt, the beginning dose should not exceed 1/200 grain (1/3 mg.). If without the desired effect it may be repeated in two hours.