The rational clinical examination. Is this patient having a myocardial infarction?

When faced with a patient with acute chest pain, clinicians must distinguish myocardial infarction (MI) from all other causes of acute chest pain. If MI is suspected, current therapeutic practice includes deciding whether to administer thrombolysis or primary percutaneous transluminal coronary angioplasty and whether to admit patients to a coronary care unit. The former decision is based on electrocardiographic (ECG) changes, including ST-segment elevation or left bundle-branch block, the latter on the likelihood of the patient's having unstable high-risk ischemia or MI without ECG changes. Despite advances in investigative modalities, a focused history and physical examination followed by an ECG remain the key tools for the diagnosis of MI. The most powerful features that increase the probability of MI, and their associated likelihood ratios (LRs), are new ST-segment elevation (LR range, 5.7-53.9); new Q wave (LR range, 5.3-24.8); chest pain radiating to both the left and right arm simultaneously (LR, 7.1); presence of a third heart sound (LR, 3.2); and hypotension (LR, 3.1). The most powerful features that decrease the probability of MI are a normal ECG result (LR range, 0.1-0.3), pleuritic chest pain (LR, 0.2), chest pain reproduced by palpation (LR range, 0.2-0.4), sharp or stabbing chest pain (LR, 0.3), and positional chest pain (LR, 0.3). Computer-derived algorithms that depend on clinical examination and ECG findings might improve the classification of patients according to the probability that an MI is causing their chest pain.

Use of Hirulog in the prevention of venous thrombosis after major hip or knee surgery

BACKGROUND

The study objective was to determine whether Hirulog, a direct thrombin inhibitor, has potential efficacy and safety in the prevention of deep vein thrombosis (DVT) in orthopedic patients. A phase 2 open-label, dose-escalating design was used to study 222 unselected patients undergoing major hip or knee surgery in tertiary-care, university-affiliated hospitals.

METHODS AND RESULTS

Subcutaneous Hirulog was initiated postoperatively. Patients were evaluated for bleeding and symptomatic pulmonary embolism, and mandatory bilateral venography was performed before discharge. Dose escalations were made on the basis of observed rates of bleeding and venous thrombosis. There were five dosage regimens used: 0.3 mg/kg every 12 hours, 0.6 mg/kg every 12 hours, 1.0 mg/kg every 12 hours for 3 days followed by 0.6 mg/kg every 12 hours for up to 11 days, 1.0 mg/kg every 12 hours, and 1.0 mg/kg every 8 hours. One hundred seventy-seven patients who had technically adequate bilateral venography or objectively documented pulmonary embolism were included in the primary analysis of efficacy. The highest dosage regimen (1.0 mg/kg every 8 hours) provided the lowest rates of total DVT (17%) and proximal DVT (2%), both of which were significantly lower (P = .010 and P = .023, respectively) than the pooled rates of total (43%) and proximal (20%) DVT seen with the first four regimens. Bleeding rates were low (< 5%) with all regimens.

CONCLUSIONS

This study demonstrates that 1.0 mg/kg Hirulog every 8 hours started postoperatively is potentially efficacious and safe for the prevention of DVT after major hip or knee surgery.

Reevaluation of the sensitivity of impedance plethysmography for the detection of proximal deep vein thrombosis

BACKGROUND

To reevaluate the sensitivity of impedance plethysmography (IPG) for proximal deep vein thrombosis (DVT) and to establish a relationship between the location and size of thrombi and the results of IPG.

DESIGN

Prospective cohort study.

METHODS

One hundred thirty-two consecutive patients with clinically suspected DVT underwent IPG testing and most (n = 118) underwent contrast-enhanced venography; in 14 patients, venous ultrasonography was performed and demonstrated definitive proximal DVT in which the size and extent of the thrombus could be delineated. All patients with dubious or normal ultrasound results underwent contrast-enhanced venography. All tests were performed and test results were interpreted without knowledge of the results of the other tests. Patients were considered to have proximal DVT if this was demonstrated on venography or ultrasound, calf DVT if this was demonstrated on venography, or no DVT if venography yielded normal findings. The sensitivity and specificity of IPG for DVT were calculated.

RESULTS

Of the 132 patients, 40 (30%) had proximal DVT, seven (5%) had calf DVT, and 85 (64%) had no DVT. The sensitivity of IPG for proximal DVT was 65% and the specificity was 93%. Of the proximal vein thrombi, IPG detected three (23%) of 13 that involved the popliteal vein but not the superficial femoral vein and 23 (85%) of 27 proximal vein thrombi that involved the superficial femoral vein.

CONCLUSIONS

Our study demonstrated that the sensitivity of IPG for proximal DVT at our center is only 65%, a figure that is much lower than those reported in earlier studies from our institution. We hypothesize that because of a change in referral practice, an increased proportion of patients with less severe symptoms are now referred to our center than in the past. These patients have thrombi that are smaller, less likely to be occlusive, and therefore less likely to yield abnormal IPG findings.

A noninvasive strategy for the treatment of patients with suspected pulmonary embolism

BACKGROUND

Pulmonary embolism has historically presented a formidable diagnostic problem because of the nonspecificity of the clinical findings associated with this disorder and the diagnostic uncertainties and challenges presented by both ventilation-perfusion lung scanning and pulmonary angiography. We have reported previously that serial noninvasive leg testing provides a practical noninvasive alternative to pulmonary angiography in patients with non-high probability (nondiagnostic) lung scans and adequate cardiorespiratory reserve. We have reevaluated this observation prospectively to (1) confirm or refute our original observation in an independent cohort and (2) to increase the numbers sufficiently to provide narrow confidence limits for the observed outcomes.

METHODS

A prospective comparative study in 1564 consecutive patients with suspected pulmonary embolism who underwent ventilation-perfusion lung scanning and objective testing for proximal-vein thrombosis.

RESULTS

On long-term follow-up of 627 patients with the following characteristics: (1) abnormal, nondiagnostic lung scans, (2) not taking anticoagulant therapy, and (3) serial noninvasive test results negative for proximal-vein thrombosis, only 12 patients (1.9%; 95% confidence limits, 0.8% to 3.0%) had venous thromboembolism. By comparison, venous thromboembolism on follow-up occurred in four (0.7%) of 586 patients (95% confidence limits, 0.02% to 1.3%) with normal lung scans in whom anticoagulant therapy was withheld and in eight (5.5%) of 145 patients (95% confidence limits, 1.8% to 9.2%) with high probability lung scans who received anticoagulant therapy.

CONCLUSIONS

Our findings indicate that the clinician has a practical noninvasive strategy in patients with adequate cardiorespiratory reserve and nondiagnostic lung scans that (1) avoids pulmonary angiography, (2) identifies patients with proximal-vein thrombosis who require treatment, and (3) avoids the need for treatment and further investigation in the majority of patients.

Optimal therapeutic level of heparin therapy in patients with venous thrombosis

BACKGROUND

Audits of heparin sodium therapy suggest that heparin administration is fraught with difficulty. The literature indicates that the current clinical practice of intuitive ordering of heparin results in inadequate therapy because of fear of bleeding. The importance of exceeding the lower limit of the therapeutic range has been strongly supported by findings of prospective clinical trials. Firm evidence indicates that failure to exceed the lower limit is associated with unacceptably high rates of recurrent venous thromboembolism. By comparison, evidence supporting the risk of exceeding the upper limit of the therapeutic range is weak.

OBJECTIVES

The purposes of this study were (1) to validate prospectively an approach designed to minimize the proportion of patients receiving subtherapeutic doses of heparin and (2) to determine the effectiveness and safety of decreasing the heparin dosage infused on the basis of activated partial thromboplastin time (APTT) prolongation reflecting both heparin and warfarin sodium effects.

METHODS

We performed a randomized double-blind study evaluating a prescriptive approach to heparin administration in patients receiving heparin or heparin with warfarin. Thromboembolic and bleeding complications were objectively documented.

RESULTS

Only 1% and 2% of patients had subtherapeutic heparin levels for 24 hours or more in the heparin and combined groups, respectively. Recurrent venous thromboembolism occurred infrequently in both groups (7%). Sixty-nine (69%) of 99 patients receiving combined therapy had supratherapeutic values, compared with 24 (24%) of 100 receiving heparin; bleeding complications occurred in 9% and 12%, respectively.

CONCLUSIONS

Our findings demonstrate that no association exists between supratherapeutic APTT responses and bleeding, which is in direct contrast to the observed association between subtherapeutic APTT responses and recurrent venous thromboembolism.

Venous thrombosis in patients who have undergone major hip or knee surgery: detection with compression US and impedance plethysmography

To compare the sensitivity, specificity, and predictive values of compression ultrasonography (US) in postoperative orthopedic patients with those of (a) impedance plethysmography in postoperative patients and (b) compression US in symptomatic outpatients, the authors performed an investigator-blinded cohort study. One hundred thirty-four consecutive inpatients who had undergone elective knee-replacement surgery or surgery for a fractured hip and 65 consecutive outpatients with clinically suspected venous thrombosis who had undergone venography were evaluated. Compression US allowed detection of 11 of 21 (52.4%) proximal-vein thrombi but was insensitive to calf-vein thrombi in the orthopedic patients. Compression US had a significantly greater specificity and positive predictive value than impedance plethysmography for all thrombi in orthopedic patients; compression US also had greater sensitivity. The sensitivity of compression US for proximal-vein thrombi was significantly higher (92.1%) in symptomatic outpatients than in orthopedic patients. The authors conclude that compression US has significant advantages over impedance plethysmography in the detection of proximal-vein thrombi in patients who have undergone hip- or knee-replacement surgery.

Heparin for 5 days as compared with 10 days in the initial treatment of proximal venous thrombosis

It is common practice to begin anticoagulant treatment of deep-vein thrombosis with a 10-day course of intravenous heparin, with warfarin added on day 5 to 10 and continued for several months. We performed a randomized, double-blind trial comparing a shorter course of continuous intravenous heparin (5 days, with warfarin sodium begun on the first day) with the conventional 10-day course of heparin (with warfarin sodium begun on the fifth day) in the initial treatment of 199 patients with acute proximal venous thrombosis documented by venography. The frequency of objectively documented recurrent venous thromboembolism was low and essentially the same in the two groups (7.1 percent in the short-course group vs. 7.0 percent in the long-course group). Because the observed difference between the groups was 0.1 percent in favor of the long-course group, it is unlikely (P less than 0.05) that a true difference in favor of this group would be greater than 7.5 percent; the difference could be as much as 7.3 percent in favor of the short-course group. Major bleeding episodes were infrequent, and the rate was similar in both groups. We conclude that a five-day course of heparin is as effective as a 10-day course in treating deep venous thrombosis. Furthermore, using the shorter course would permit earlier discharge from the hospital and thus offer substantial cost savings.

Clinical validity of a normal perfusion lung scan in patients with suspected pulmonary embolism

The objective of this study was to test the safety of withholding anticoagulant therapy in patients with clinically suspected pulmonary embolism who have normal perfusion lung scans, regardless of the clinical manifestations. Anticoagulant therapy was withheld or withdrawn in 515 consecutive patients except in patients in whom deep-vein thrombosis was detected. Only three of the 515 patients had symptomatic venous thromboembolism on follow-up. The frequency of symptomatic pulmonary embolism on follow-up was one of 515 patients. With knowledge of the normal findings by perfusion scanning, an alternative diagnosis was established in 367 of the 515 patients. Cause of symptoms remained uncertain in 148 patients. It is safe to withhold anticoagulant therapy in patients with suspected pulmonary embolism and normal perfusion scans, regardless of the clinical manifestations. The finding of a normal perfusion scan excludes the presence of clinically important pulmonary embolism and makes pulmonary angiography unnecessary.

A new noninvasive management strategy for patients with suspected pulmonary embolism

Pulmonary embolism is associated strongly with proximal-vein thrombosis. We tested the hypothesis that recurrent venous thromboembolism is unlikely in the absence of proximal-vein thrombosis. We performed a prospective cohort study in 874 patients with suspected pulmonary embolism. On long-term follow-up of 371 patients with the following characteristics: (1) abnormal, non-high-probability lung scans, (2) off anticoagulant therapy, and (3) serial noninvasive test results negative for proximal-vein thrombosis, only 10 (2.7%; 95% confidence limits, 1.3% to 4.9%) had venous thromboembolism. By comparison, venous thromboembolism on follow-up occurred in 3 (1%) of 315 patients (95% confidence limits, 0.2% to 2.8%) with normal lung scans, and in 5 (7%) of 66 patients (95% confidence limits, 2.5% to 16.8%) with high-probability lung scans. Patients whose serial noninvasive test results were negative for proximal-vein thrombosis have a good prognosis without anticoagulant therapy.