Chapter 21 Marini Acute Coronary Syndromes

453

CHAPTER 21 • Acute Coronary Syndromes

should not be used in STEMI patients present- ing greater than 24 hours of onset of symptoms. Fibrinolytic therapy should be given within 30 minutes of arrival in the emergency room (door- to-needle time of ≤ 30 minutes), once a decision for their use has been made. It is also recom- mended that patients receiving fibrinolytic ther- apy should be transferred to a facility with PCI availability as soon as possible. Such transfer has been shown to be generally safe. • Antithrombotic therapy with fibrinolytic therapy: UFH is used with fibrin-specific agents (t-PA, TNK-tPA, and r-PA). It is generally not recom- mended with SK. It is given in a bolus dose of 60 units/kg (4,000 units maximum), followed by an infusion of 12 units/kg/h (1,000 units/h maximum). The dose of the infusion should be adjusted to keep PTT 1.5 to 2.0 times the upper limit of normal. The infusion is usually continued for 48 hours postfibrinolytic therapy. Heparin infusion should be continued beyond 48 hours if patients are at high risk for venous or systemic thromboembolic events (large ante- rior MI, severe LV dysfunction, CHF, thrombi in the LV, AF). Patients must be started on warfa- rin, and the heparin should be discontinued only once INR is greater than 2. • Gp2b/3a receptor antagonists can be used with half-dose r-PA or TNK-tPA in patients below 70 years of age. In older patients, this combination increases the risk of bleeding. • The limitations of fibrinolytic therapy include the following: (1) 20% to 30% patients have contrain- dications for thrombolytic therapy; (2) 50% to 70% patients have successful reperfusion; (3) recurrent ischemia or reinfarction is seen in 15% to 30% patients who experienced successful reperfusion; and (4) 4% to 5% patients experience major bleed- ing, including 0.7% to 1.5% risk of intracerebral hemorrhage (which has a high fatality rate). • Indicators of successful reperfusion: significant improvement or complete disappearance of chest pain along with greater than 50% resolution of ST segment elevation on ECG within 90 min- utes of administration of fibrinolytic therapy. The greater the degree of improvement of ST seg- ment change, the better the long-term outcome. C omplications of F ibrinolytics 1. Hemorrhage: Four to five percent of patients experience major bleeding (usually GI) and

• All STEMI patient subgroups (age, gender, comorbid conditions) and infarct locations seem to benefit from fibrinolytic therapy when PCI is not available or delayed. The prior administration of fibrinolytic does not preclude subsequent PCI. • Proportionately, the greatest benefits are expe- rienced by patients at greatest risk: those with larger and anterior infarctions, those with new LBBB, and those in CHF. • The benefit with fibrinolytic therapy is time- dependent . For every 1,000 patients treated with fibrinolytics (compared to placebo), 65 lives were saved if treated within first hour of onset of symptoms, 26 lives if treated within 1 to 3 hours of onset of symptoms, and 18 lives if treated within 6 to 12 hours of onset of symptoms. • Fibrinolytic therapy should be given to STEMI patients without contraindications within 12 hours of the onset of chest pain and if the esti- mated door–balloon time is greater than 90 minutes (absence of immediate PCI availability). Patients seen within 12 to 24 hours of onset of chest pain and with ongoing chest pain and persistent ST elevations may also be considered for fibrinolytic therapy if PCI is unavailable, but the magni- tude of benefit is significantly lower. Fibrinolytic Remote history of stroke or transient ischemic attack Recent prolonged (>10 minutes) cardiopulmonary resuscitation Needle puncture of a noncompressible vessel Intracardiac thrombus CNS, central nervous system. Table 21-4.  Contraindications to Thrombolytic Therapy ABSOLUTE CONTRAINDICATIONS Active internal bleeding History of CNS disease (stroke, arteriovenous malformation, surgery, tumor, or head trauma) within 6 months Hemorrhagic CVA anytime in the past Suspected aortic dissection Underlying coagulopathy, including thrombocytopenia Ongoing warfarin therapy with INR > 2.5 Severe diastolic hypertension (diastolic blood pressure >110 mm Hg) Recent (2–4 weeks) trauma, deep tissue biopsy, or operation Pregnancy RELATIVE CONTRAINDICATIONS Systolic blood pressure >180 mm Hg