Morbidity, mortality and economic burden of renal impairment in cardiac intensive care

BACKGROUND

Moderate to severe impairment of renal function has emerged as a potent risk factor for adverse short- and long-term outcomes among patients presenting with cardiac disease.

AIMS

We sought to define the clinical, late mortality and economic burden of this risk factor among patients presenting to cardiac intensive care.

METHODS

A clinical audit of patients presenting to cardiac intensive care was undertaken between July 2002 and June 2003. All patients presenting with cardiac diagnoses were included in the study. Baseline creatinine levels were assessed in all patients. Late mortality was assessed by the interrogation of the National Death Register. Renal impairment was defined as estimated glomerular filtration rate <60 mL/min per 1.73 m2, as calculated by the Modified Diet in Renal Disease formula. In-hospital and late outcomes were compared by Cox proportional hazards modelling, adjusting for known confounders. A matched analysis and attributable risk calculation were undertaken to assess the proportion of late mortality accounted for by impairment of renal function and other known negative prognostic factors. The in-hospital total cost associated with renal impairment was assessed by linear regression.

RESULTS

Glomerular filtration rate <60 mL/min per 1.73 m2 was evident in 33.0% of this population. Among these patients, in-hospital and late mortality were substantially increased: risk ratio 13.2; 95% CI 3.0-58.1; P < 0.001 and hazard ratio 6.2; 95% CI 3.6-10.7; P < 0.001, respectively. In matched analysis, renal impairment to this level was associated with 42.1% of all the late deaths observed. Paradoxically, patients with renal impairment were more conservatively managed, but their hospitalizations were associated with an excess adjusted in-hospital cost of $A1676.

CONCLUSION

Impaired renal function is associated with a striking clinical and economic burden among patients presenting to cardiac intensive care. As a marker for future risk, renal function accounts for a substantial proportion of the burden of late mortality. The burden of risk suggests a greater potential opportunity for improvement of outcomes through optimisation of therapeutic strategies.

Survival outcomes 1 year after reperfusion therapy with either alteplase or reteplase for acute myocardial infarction: results from the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO) III Trial

BACKGROUND

New recombinant plasminogen activators have been developed to simulate the fibrinolytic action of the physiological serine protease tissue plasminogen activator (alteplase, t-PA), and have prolonged half-life features permitting bolus administration. One such activator, reteplase (r-PA), was compared with t-PA in the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO)-III Trial.

METHODS AND RESULTS

At 1-year follow-up, survival status was ascertained in 97.4% of the 15 059 patients enrolled in the GUSTO-III trial. At 1 year, the mortality rate for the t-PA-assigned group was 11.06%, and for r-PA it was 11.20% (P:=0. 77). The absolute mortality difference of 0.14% has 95% CIs of -1. 21% to 0.93%. There were no significant differences in outcome by intention-to-treat for the 2 different plasminogen activators in the prespecified groups (age, infarct location, time-to-treatment). The absolute difference in mortality rates between t-PA and r-PA progressively narrowed over the predetermined observation times after random assignment; it was 0.31% at 24 hours, 0.26% at 7 days, 0.23% at 30 days, and 0.14% at 1 year. Of note, mortality rate in the trial between 30 days and 1 year in 13 883 patients was 4.02% and did not differ between the treatment groups. However, this mortality rate was substantially greater than in GUSTO-I, in which mortality rate for t-PA versus streptokinase between 30 days and 1-year was 2.97% (heart rate 1.36, 95% CI 1.23, 1.50, P:<0.001).

CONCLUSIONS

The r-PA and t-PA strategies yielded similar survival outcomes after 30 days in this trial. The increase in mortality rate during extended follow-up compared with previous trials may reflect higher-risk patients and highlights the need for improved secondary prevention strategies.

Single-bolus tenecteplase compared with front-loaded alteplase in acute myocardial infarction: the ASSENT-2 double-blind randomised trial

BACKGROUND

Bolus fibrinolytic therapy facilitates early efficient institution of reperfusion therapy. Tenecteplase is a genetically engineered variant of alteplase with slower plasma clearance, better fibrin specificity, and high resistance to plasminogen-activator inhibitor-1. We did a double-blind, randomised, controlled trial to assess the efficacy and safety of tenecteplase compared with alteplase.

METHODS

In 1021 hospitals, we randomly assigned 16,949 patients with acute myocardial infarction of less than 6 h duration rapid infusion of alteplase (< or = 100 mg) or single-bolus injection of tenecteplase (30-50 mg according to bodyweight). All patients received aspirin and heparin (target activated partial thromboplastin time 50-75 s). The primary outcome was equivalence in all-cause mortality at 30 days.

FINDINGS

Covariate-adjusted 30-day mortality rates were almost identical for the two groups--6.18% for tenecteplase and 6.15% for alteplase. The 95% one-sided upper boundaries of the absolute and relative differences in 30-day mortality were 0.61% and 10.00%, respectively, which met the prespecified criteria of equivalence (1% absolute or 14% relative difference in 30-day mortality, whichever difference proved smaller). Rates of intracranial haemorrhage were similar (0.93% for tenecteplase and 0.94% for alteplase), but fewer non-cerebral bleeding complications (26.43 vs 28.95%, p=0.0003) and less need for blood transfusion (4.25 vs 5.49%, p=0.0002) were seen with tenecteplase. The rate of death or non-fatal stroke at 30 days was 7.11% with tenecteplase and 7.04% with alteplase (relative risk 1.01 [95% CI 0.91-1.13]).

INTERPRETATION

Tenecteplase and alteplase were equivalent for 30-day mortality. The ease of administration of tenecteplase may facilitate more rapid treatment in and out of hospital.

Sex, clinical presentation, and outcome in patients with acute coronary syndromes. Global Use of Strategies to Open Occluded Coronary Arteries in Acute Coronary Syndromes IIb Investigators

BACKGROUND

Studies have reported that women with acute myocardial infarction have in-hospital and long-term outcomes that are worse than those of men.

METHODS

To assess sex-based differences in presentation and outcome, we examined data from the Global Use of Strategies to Open Occluded Coronary Arteries in Acute Coronary Syndromes IIb study, which enrolled 12,142 patients (3662 women and 8480 men) with acute coronary syndromes, including infarction with ST-segment elevation, infarction with no ST-segment elevation, and unstable angina.

RESULTS

Overall, the women were older than the men, and had significantly higher rates of diabetes, hypertension, and prior congestive heart failure. They had significantly lower rates of prior myocardial infarction and were less likely ever to have smoked. A smaller percentage of women than men had infarction with ST elevation (27.2 percent vs. 37.0 percent, P<0.001), and of the patients who presented with no ST elevation (those with myocardial infarction or unstable angina), fewer women than men had myocardial infarction (36.6 percent vs. 47.6 percent, P<0.001). Women had more complications than men during hospitalization and a higher mortality rate at 30 days (6.0 percent vs. 4.0 percent, P<0.001) but had similar rates of reinfarction at 30 days after presentation. However, there was a significant interaction between sex and the type of coronary syndrome at presentation (P=0.001). After stratification according to coronary syndrome and adjustment for base-line variables, there was a nonsignificant trend toward an increased risk of death or reinfarction among women as compared with men only in the group with infarction and ST elevation (odds ratio, 1.27; 95 percent confidence interval, 0.98 to 1.63; P=0.07). Among patients with unstable angina, female sex was associated with an independent protective effect (odds ratio for infarction or death, 0.65; 95 percent confidence interval, 0.49 to 0.87; P=0.003).

CONCLUSIONS

Women and men with acute coronary syndromes had different clinical profiles, presentation, and outcomes. These differences could not be entirely accounted for by differences in base-line characteristics and may reflect pathophysiologic and anatomical differences between men and women.

Can we improve on front-loaded alteplase (r-TPA)?

The method of administration of alteplase has evolved since its introduction to clinical practice in the late 1980s. The initial dosage regimen of a graded administration of 100 mg was replaced by the front-loaded weight adjusted regimen, the efficacy of which was demonstrated in the GUSTO 1 trial. Double bolus administration was shown to achieve superior TIMI 3 patency of the infarct related artery in a small angiographic study, but the COBALT trial failed to show equivalence and indeed showed a slightly higher mortality and incidence of stroke, so cannot be recommended. Reteplase, a deletion mutant of alteplase, also showed superior efficacy in achieving coronary patency but no clinical superiority in outcomes in the 15,000 patient GUSTO 3 trial. The case of administration of reteplase, however, has some attraction as an alternative to alteplase. Trials of newer agents based on further modifications of alteplase are ongoing, but at present the front-loaded alteplase regimen remains the standard for clinical practice.

The GUSTO 2b and related studies. Global Use of Strategies to Open Occluded Coronary Arteries

Direct anti-thrombin inhibitors such as hirudin have theoretical advantages over heparin. Two large studies in acute coronary syndromes were designed to test the thrombin hypothesis by demonstrating improved outcomes in hirudin treated patients. TIMI 9 assessed the effect of hirudin in patients with ST elevation receiving thrombolytic therapy. GUSTO 2 assessed the full spectrum of acute coronary syndromes of ST elevation and non-ST elevation. Over 15,000 patients were entered into the studies and no major benefit was demonstrated for hirudin. This may, however, relate to endpoints measured and the timing of the anti-thrombin.

Hirudin (desirudin) and Hirulog (bivalirudin) in acute ischaemic syndromes and the rationale for the Hirulog/Early Reperfusion Occlusion (HERO-2) Study

Unlike unfractionated heparin, direct thrombin inhibitors such as hirudin and Hirulog inhibit clot-bound as well as fluid-phase thrombin, escape neutralisation by platelet secretion products, do not require monitoring, and are unassociated with immune thrombocytopenia. They have been shown to have modest advantages over heparin when given after thrombolytic therapy, reducing reinfarction by 14%. In the Global Use of Strategies to Open Occluded Coronary Arteries (GUSTO 2b) trial, patients treated with streptokinase and adjunctive hirudin had a reduction in death or myocardial infarction of 40% at 30 days (8.6% with hirudin versus 14.4% with heparin, p = 0.004). In the Hirulog Early Reperfusion/Occlusion (HERO 1) trial, 48% of patients who received Hirulog as adjunctive therapy with streptokinase had Thrombolysis in Myocardial Infarction (TIMI) trial grade 3 flow in the infarct-related artery, compared with 35% of patients who received heparin with streptokinase (p < 0.05). The HERO 2 study, involving 17,000 patients, will test the hypothesis that Hirulog and aspirin given before streptokinase will reduce mortality compared with aspirin plus heparin. Early administration of direct thrombin inhibitors may potentially improve the outcome of patients treated with thrombolytic therapy.

The current status of thrombolytic therapy

Fibrinolytic therapy substantially reduces mortality from acute myocardial infarction. Patient selection is, however, important. The patient must present within 12 hours of the onset of ischaemic symptoms, have definite ECG changes of ST elevation or left bundle branch block and no contraindications. The major contraindications are those for risk of an intracerebral bleed, recent stroke, intracranial tumour or risk of a major systemic bleed. Age and hypertension are not contraindications but may modify the regimen used. Heparin is required with recombinant tissue plasminogen activator but is optional with streptokinase. The recent COBALT trial suggests that the accelerated weight related t-PA regimen given over 90 minutes is more satisfactory than double bolus t-PA. However, in patients under 75 years of age, the two regimens were equivalent. For patients suffering acute myocardial infarction, practitioners should now individualise choice of therapy, rather than give the same cocktail to all patients. The choice of regimen will depend on the cardiac risk, the stroke risk, the bleeding risk and the cost.

Investigating chest pain

Chest pain is a common complaint that in many patients requires full investigation to exclude the possibility of heart disease. Simple tests such as ECG and chest X-ray are often unhelpful. The main investigation is an exercise test but interpretation of this is not simple and its usefulness is limited in middle-aged women. More sophisticated imaging such as thallium scanning and stress echocardiography are of limited additional benefit and have significant cost. Coronary angiography remains the gold standard for the assessment of coronary atherosclerosis.

Evaluation of paradoxic beneficial effects of smoking in patients receiving thrombolytic therapy for acute myocardial infarction: mechanism of the "smoker's paradox" from the GUSTO-I trial, with angiographic insights. Global Utilization of Streptokinase and Tissue-Plasminogen Activator for Occluded Coronary Arteries

OBJECTIVES

Our purpose was to evaluate the relation between smoking and the outcomes of patients receiving thrombolysis for acute myocardial infarction.

BACKGROUND

A paradoxic beneficial effect has been observed in smokers with a myocardial infarction. We analyzed outcomes and baseline characteristics of 11,975 nonsmokers, 11,117 ex-smokers and 17,507 current smokers in a multinational trial of thrombolysis for acute myocardial infarction.

METHODS

Patients were randomized to one of four thrombolytic protocols. An angiographic substudy in 2,431 patients evaluated reperfusion, reocclusion and ventricular function. Effects of smoking were evaluated by logistic regression analysis after adjustment for age and gender. A mortality model evaluated the simultaneous effect of baseline characteristics on the prognostic importance of smoking. These processes were performed with data from both the main trial and the angiographic substudy; then angiographic factors (coronary anatomy, patency and ejection fraction) were added to the model.

RESULTS

Smokers were significantly younger by a mean of 11 years) and had less comorbidity or severe coronary artery disease than nonsmokers. Nonsmokers had significantly higher hospital and 30-day mortality rates (9.9% and 10.3%, respectively) than smokers (3.7% vs. 4%, respectively, both p < 0.001) and more in-hospital complications. The unadjusted odds ratio for 30-day mortality in nonsmokers was 3.36 (95% confidence interval [CI] 2.08 to 5.41), 1.21 (95% CI 0.71 to 2.08) after adjustment for age and gender and 1.08 (95% CI 0.59 to 1.96) after adjustment for all clinical baseline characteristics.

CONCLUSIONS

Smokers receiving thrombolysis for acute myocardial infarction presented 11 years earlier than nonsmokers, which generally accounted for their better outcome. When other differences in clinical and angiographic baseline factors and therapeutic responses were evaluated, no significant difference in mortality was seen between smokers and nonsmokers.

Predictors of 30-day mortality in the era of reperfusion for acute myocardial infarction. Results from an international trial of 41,021 patients. GUSTO-I Investigators

BACKGROUND

Despite remarkable advances in the treatment of acute myocardial infarction, substantial early patient mortality remains. Appropriate choices among alternative therapies and the use of clinical resources depend on an estimate of the patient's risk. Individual patients reflect a combination of clinical features that influence prognosis, and these factors must be appropriately weighted to produce an accurate assessment of risk. Prior studies to define prognosis either were performed before widespread use of thrombolysis or were limited in sample size or spectrum of data. Using the large population of the GUSTO-I trial, we performed a comprehensive analysis of relations between baseline clinical data and 30-day mortality and developed a multivariable statistical model for risk assessment in candidates for thrombolytic therapy.

METHODS AND RESULTS

For the 41,021 patients enrolled in GUSTO-I, a randomized trial of four thrombolytic strategies, relations between clinical descriptors routinely collected at initial presentation, and death within 30 days (which occurred in 7% of the population) were examined with both univariable and multivariable analyses. Variables studied included demographics, history and risk factors, presenting characteristics, and treatment assignment. Risk modeling was performed with logistic multiple regression and validated with bootstrapping techniques. Multivariable analysis identified age as the most significant factor influencing 30-day mortality, with rates of 1.1% in the youngest decile (< 45 years) and 20.5% in patients > 75 (adjusted chi 2 = 717, P < .0001). Other factors most significantly associated with increased mortality were lower systolic blood pressure (chi 2 = 550, P < .0001), higher Killip class (chi 2 = 350, P < .0001), elevated heart rate (chi 2 = 275, P < .0001), and anterior infarction (chi 2 = 143, P < .0001). Together, these five characteristics contained 90% of the prognostic information in the baseline clinical data. Other significant though less important factors included previous myocardial infarction, height, time to treatment, diabetes, weight, smoking status, type of thrombolytic, previous bypass surgery, hypertension, and prior cerebrovascular disease. Combining prognostic variables through logistic regression, we produced a validated model that stratified patient risk and accurately estimated the likelihood of death.

CONCLUSIONS

The clinical determinants of mortality in patients treated with thrombolytic therapy within 6 hours of symptom onset are multifactorial and the relations complex. Although a few variables contain most of the prognostic information, many others contribute additional independent prognostic information. Through consideration of multiple characteristics, including age, medical history, physiological significance of the infarction, and medical treatment, the prognosis of an individual patient can be accurately estimated.

GUSTO II trial

The GUSTO II trial will investigate the role of antithrombin therapy in acute coronary syndromes, comparing standard doses of heparin with the specific antithrombin agent recombinant hirudin. The two drugs will be compared as primary therapy in patients with unstable angina or patients with myocardial infarction (MI) unsuitable for thrombolysis, and as post thrombolysis treatment in patients who fulfil standard criteria for thrombolysis therapy. A total of 12,000 patients will be studied in a global, multifactorial trial.

The GUSTO trial: background and baseline characteristics

The GUSTO study was designed to test the hypothesis that achieving early sustained patency with a thrombolytic regimen in acute coronary thrombosis would improve mortality. Four regimens were compared. In 41,021 patients randomised, nearly 3000 of these were in Australia and New Zealand. These regimens were streptokinase (SK) with subcutaneous heparin (9841 patients), SK and intravenous heparin (10,410 patients), accelerated tissue plasminogen activator (t-PA) and intravenous heparin (10,396 patients) and combined SK and t-PA (10,374 patients). The patients were well matched for baseline characteristics. The mean time to treatment was two hours. The accompanying regimen of investigation and revascularisation was aggressive--58% receiving angiography (28% in Australia), 15% angioplasty (5% in Australia) and 9% bypass surgery (4% in Australia). The GUSTO trial results should be interpreted in the light of these background observations.

Complications of defibrillation with permanent pacemaker in situ

A permanent demand pacing generator was implanted in the right deltopectoral fossa with unipolar transvenous lead advanced to the right ventricle. Implant and subsequent pacing parameters were normal. Five days later an emergency DC cardioversion was performed with one paddle 2 inches from the generator. Cardioversion was followed by failure of QRS-sensing and, at immediate explant, rise in stimulation threshold. The pulse generator showed end-of-life characteristics. The patient died 4 days following replacement of the generator and lead. At autopsy, right ventricular infarction was found, presumably relating to current discharge along the lead. Pacemaker analysis showed damage to the protection zener diode and oscillator integrated circuit of the generator during cardioversion.