Nonlinear transformation of the resting electrocardiogram in the diagnosis of coronary artery disease.

Despite the common use of the standard 12-lead ECG, its reliability as an indicator of coronary artery disease (CAD) is poor. The normal ECG is falsely negative in more than 50% of angiographically proven CAD. The waveform of the standard ECG, however, can be transformed mathematically by nonlinear signal transformation to enhance its interpretation by computer. Using such a process it is possible that abnormalities can be identified in "normal" ECGs that can be correlated with CAD, thus identifying high-risk patients. A computer template that represents grouped data of normal ECGs for patients who also have normal coronary angiography was developed. Unblinded, preliminary testing of the template on normal ECGs of 107 white patients who had normal or abnormal coronary angiograms was performed. The process identified presence or absence of CAD with 82% specificity and 71% sensitivity for 53 women, and with 82% specificity and 86% sensitivity for 54 men. These preliminary results are promising, but further refinement of the templates is required and blinded studies with larger numbers and varieties of patients are needed.

Diagnosis of complex acid-base disorders: physician performance versus the microcomputer.

Patients with acid-base disturbances that are often complex frequently present to the emergency department. The sometimes hectic nature of the ED can preclude the appropriate quantitative analysis required by these disorders, especially when mixed disturbances are present. A computer program using generally accepted acid-base and electrolyte formulae was developed for use on the Apple II+ or IBM-PC microcomputer. Each of a series of 35 acid-base disturbances incorporating single, double, and triple disorders was correctly identified by the computer in less than 45 seconds. Problem sets based on the same 35 disturbances were presented to 21 physician-subjects at various levels of training from the emergency medicine, internal medicine, pediatrics, surgery, and family practice specialties. Although the physicians were given unlimited time and the necessary formulae to reach a diagnosis, they were requested to perform their analyses in the same fashion used in the ED. Although times varied widely, no physician spent more than five minutes on any problem. The physician correct response rates were 86%, 49%, and 17% for single, double, and triple disorders, respectively. The primary disorder correct response rate was 89% for double disorders and 94% for triple disorders. The primary and secondary disorder correct response rate was 58% for triple disorders. The data suggest that the microcomputer may be beneficial in the rapid assessment of complex disorders.

Renal artery obstruction.

A 57-year-old woman with an extensive cardiac history presented complaining of left flank pain. An intravenous pyelogram performed for the presumptive diagnosis of renal calculus showed poor function of the left kidney. Angiography demonstrated a 95% obstructing embolus in the left renal artery, which was removed surgically. This case illustrates some of the pitfalls in the diagnosis of renal artery obstruction and the need for a high index of suspicion. The intrarenal infusion of thrombolytic agents such as streptokinase may become the treatment of choice despite the success of surgical embolectomy. The diagnosis, laboratory analysis, and treatment of renal artery obstruction is discussed.

Pancreatic injury associated with interposed abdominal compressions in pediatric cardiopulmonary resuscitation.

A case in which conventional CPR was augmented with interposed abdominal compressions on a child is reported. Animal studies and electrical models of this new form of CPR have demonstrated improved hemodynamics without instance of intra-abdominal injury. In this case, intraperitoneal visceral injury was noticed in the form of blood within the stomach and small intestine and parenchymal hemorrhage within the pancreas. Similar pancreatic injury has not been reported with conventional pediatric CPR, and caution may have to be exercised if this form of CPR with interposed abdominal compressions is to be used on children.

Doppler ultrasound monitoring of systemic blood flow during CPR.

During cardiopulmonary resuscitation in 12 patients, Doppler ultrasound monitoring of radial arterial flow provided an audible, instantaneous flow sound to which the resuscitation team referred, along with the monitor electrocardiogram (EKG), in determining hemodynamic status. Incidental to the resuscitation effort, a separate analog flow signal and the monitor EKG were simultaneously recorded in eight patients. Doppler blood flow monitoring allowed evaluation of effectiveness of cardiac massage; immediate recognition of electromechanical dissociation; rapid determinations of blood pressure, often during profound hypotension, and estimates of changes in cardiac output. When the hemodynamic consequences were immediately obvious, both ineffective chest compression and pauses longer than five seconds during effective chest compression were not tolerated by those in attendance, for whom the Doppler flow signal often became the primary reference in determining the patient's cardiac status.