Calcium antagonists and stunned myocardium: importance for clinicians?

Massive diltiazem overdose treated with extracorporeal membrane oxygenation

OBJECTIVE

To describe a case of massive diltiazem overdose with a good outcome achieved after early and aggressive supportive therapy.

DESIGN

Case report.

SETTING

Pediatric Critical Care Unit.

PATIENT

Sixteen-year-old adolescent girl.

MEASUREMENTS AND MAIN RESULTS

A 16-yr-old adolescent girl presented to the emergency department 6 hrs after the intentional ingestion of 40 300-mg sustained-release diltiazem tablets (12 g of Cardura CD). She was hypotensive and required a glucagon and epinephrine infusion despite initial fluid resuscitation with saline and intravenous calcium (1 g). Multiple asystolic cardiac arrests ensued which became increasingly refractory to high-dose epinephrine. Hemodynamic support was achieved with a 48-hr period of extracorporeal membrane oxygenation for atrial standstill. Severe multiorgan dysfunction ensued (cardiac, neurologic, renal, hepatic, gastrointestinal, hematologic, and metabolic). Plasma diltiazem and its metabolites were measured and its half-life was reported between 28 and 48 hrs. A sustained decline in plasma diltiazem levels and its metabolites was not observed after two periods of charcoal hemoperfusion. Recovery of organ function occurred with sinus rhythm noted on the ninth day. The patient made a full recovery and was discharged from the critical care unit after 15 days.

CONCLUSIONS

Although massive calcium channel blocker overdose can produce profound and prolonged cardiac or multiorgan dysfunction, its toxic effects may be reversible. Supportive therapy, particularly of the cardiovascular system, is the most important goal.

Myocardial stunning--are calcium antagonists useful?

Considerable data support the point of view that calcium antagonists, whether given before the onset of ischemia or exactly at the time of reperfusion, ameliorate stunning. Benefit after the onset of reperfusion is much more controversial. It is proposed that the mechanisms whereby calcium antagonists act vary between these situations. When given before or at the onset of ischemia, then an antiischemic effect is likely. According to the hypothesis that the severity of ischemic damage determines the severity of reperfusion damage, the calcium antagonists indirectly lessen reperfusion damage. When given exactly at the time of reperfusion, the proposal is that the calcium antagonists are specifically limiting the entry of calcium ions via the calcium channel and thereby diminishing pathogenic cytosolic calcium oscillations. The reported benefit of calcium antagonists when given postreperfusion to the heart in situ, in the presence of established stunning, is of unknown mechanism and controversial significance. The hypothesis of a two-stage model of stunning with calcium as a pathogen is in accord with most of the available evidence.

Left ventricular function and prognosis after myocardial infarction: rationale for therapeutic strategies

Prognosis after acute myocardial infarction is strongly associated with left ventricular dysfunction. However, asynergy does not necessarily imply loss of viability and myocardial necrosis. In fact, two different patterns of contractile dysfunction, possibly coexisting, have been shown after acute myocardial infarction: Stunning and hibernation represent distinct patterns of contractile dysfunction that share the character of reversibility. It is noteworthy, then, to identify the presence of these two conditions at the bedside and to develop medical treatment to effect recovery of myocardial dysfunction. This strategy has the potential to ameliorate the outcome of patients after acute myocardial infarction by improving left ventricular function. Beta-blocker therapy significantly reduces mortality and the incidence of reinfarction after an acute myocardial infarction: These benefits result from the prevention of sudden death, the reduction of the extent of myocardial injury during the acute phase, and a further antiischemic action. Nevertheless, beta-blocker therapy increases left ventricular dilatation. Recent experimental and clinical data show that ACE inhibitors confer positive therapeutic effects after myocardial infarction by reducing the extent of left ventricular dilation, by reducing mortality, and by improving the clinical outcome. Not all patients, however, can be subjected to this therapeutical approach because of the possible detrimental effects produced by hypotension and by block of neurohormonal activation, sometimes truly compensatory in the early phase. Therefore, it would be interesting to suggest a combination therapy of a beta-blocker with a vasodilator agent (ACE inhibitor or calcium-channel blocker.