Complications of Tachycardia

Myocardial depletion and cardiovascular failure

Long-standing tachycardia causes permanent hyperstimulation of the heart muscle. This condition inevitably leads to the rapid depletion of cardiomyocyte reserves and a decrease in their functional activity.

A striking example of this process is Graves' disease, in which a specific syndrome develops — "thyrotoxic heart". The pathogenesis of this complication includes several successive stages:

• Development of pronounced hypertrophy of the cardiac muscle tissue.
• Transition of hypertrophy into deep dystrophy of cardiomyocytes due to a lack of energy resources.
• Occurrence of severe rhythm disturbances, in particular, atrial fibrillation.
• Final formation of severe cardiovascular failure against the background of absolute myocardial exhaustion.

Acute hemodynamic shifts and pulmonary edema

Heart rhythm disturbances and tachycardia can act as both a manifestation and the main cause of acute cardiovascular failure. This process is particularly rapid in elderly patients, individuals with severe comorbidities, and against the background of uncompensated blood loss or severe water-electrolyte shifts.

The drop in left ventricular pumping function due to exhaustion leads to blood stasis. Clinically and hemodynamically, this is reflected by a persistent increase in central venous pressure (CVP). This indicator is a critical marker of left ventricular failure and serves as a direct precursor to the development of pulmonary edema — a condition requiring emergency medical care.

Extreme conditions: thyrotoxic crisis

The extreme severity of the pathological process accompanied by extreme tachycardia is a thyrotoxic crisis. It occurs with a sudden, avalanche-like release of hormones into the bloodstream.

In this critical situation, the heart rate can reach incredible values — up to 200 beats per minute. Such ultra-high tachycardia is accompanied by a complex of severe symptoms:

1. Pronounced hyperthermia.
2. Severe nervous agitation, which can rapidly progress to a comatose state.
3. Total multiple organ failure.

In addition, against the background of the complete exhaustion of the body's compensatory mechanisms during this period, the risk of developing a severe secondary infection is extremely high, which further worsens the prognosis.

Iatrogenic causes: hypervitaminosis D

An increase in heart rate and the development of arrhythmias can be the result of medical intervention. A telling example is cholecalciferol therapy.

Overdose of active forms of vitamin D provokes the development of hypervitaminosis and subsequent severe hypercalcemia. It is precisely the excess content of calcium in the blood that becomes a trigger for critical heart rhythm disorders, including extrasystole and tachycardia. Additionally, this process is accompanied by the development of convulsive syndrome, severe nausea, fever, and general weakness.

Principles of pharmacological correction

Management of complications of tachycardia and acute heart failure requires a strictly individualized approach to each patient. To stabilize the heart rhythm and maintain myocardial function, combination therapy is used, including antiarrhythmic drugs, cardiac glycosides, and coronary vasodilators.

In the event of progressing left ventricular failure and the development of pulmonary edema, ganglion blockers and diuretics are immediately included in the regimen. A specific and vital measure in pulmonary edema is oxygen therapy — the inhalation of oxygen pre-moistened with alcohol, which is necessary to destroy foam in the airways.

Class and exam questions

What else to study on this topic

• Pathogenesis of acute adrenal insufficiency following thyroid surgery.
• Mechanisms of convulsive syndrome and fever formation in hypercalcemia caused by cholecalciferol overdose.
• Detailed clinical picture of thyrotoxic crisis and mechanisms of multiple organ failure development.
• The role of compensatory immune mechanism exhaustion in the onset of severe secondary infections in hyperthyroidism.
• Principles of individual selection of cardiac glycosides, antiarrhythmic, and coronary vasodilator drugs in circulatory failure.

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.