Identification of calcified intracardiac lesions using gradient echo MR imaging.

Gradient echo signal imaging (GEI) has expanded the clinical role of magnetic resonance (MR) imaging of the heart. The role of GEI to evaluate intracardiac calcified lesions was studied. All patients were imaged with both conventional spin echo (SE) techniques and GEI. The GEI demonstrated that calcific cardiac lesions exhibit magnetic susceptibility differences and produce marked hypointensity throughout the calcified area. All patients had echocardiographic and fluoroscopic evidence of cardiac calcification and surgical confirmation of calcified lesions. The SE MR was unable to define the intracardiac calcification. Gradient echo imaging may be a helpful adjunct in the complete definition of intracardiac calcific lesions. When profound signal void areas are detected on cardiac GEI studies, calcification should be suspected.

MR imaging in the definition of coronary artery anomalies.

Coronary angiography remains the standard imaging technique to study coronary artery anatomy. Coronary artery aneurysms and fistulas are often incompletely visualized with routine angiography. Magnetic resonance (MR) imaging of such coronary anomalies is presented. The MR images improve the preoperative assessment of patients with coronary artery aneurysms and fistulas.

Postoperative evaluation of ascending aortic prosthetic conduits by magnetic resonance imaging.

Operative repair of ascending thoracic aortic dissection and aneurysm often involves the placement of prosthetic aortic conduits and stents with wrapping of the native aorta around the prosthetic device. Postoperative assessment has been clinical because of the absence of an adequate noninvasive imaging modality and a reluctance to perform invasive contrast aortography. Magnetic resonance imaging was performed on ten patients after operative placement of a prosthetic ascending aortic graft. The MR images were reviewed and a grading system was devised based on appearance of the operative site. An increase in MR signal was noted in some patients between the graft and wrapped native vessel. In 20 percent of patients vascular lumen compromise was noted. Magnetic resonance imaging offers a noninvasive technique to assess postoperative complications and offers a viable alternative to invasive contrast aortography.

Polymorphic ventricular tachycardia.

The case of a patient with torsade de pointes in the setting of congenital complete heart block is described. Lack of recognition of this polymorphic ventricular tachycardia resulted in therapy that potentiated the dysrhythmia. After correct recognition, and directed therapy, the patient responded appropriately. The clinical settings, recognition, and management options available for torsade de pointes are discussed to familiarize the emergency physician with this important and unique dysrhythmia.

Prevention of ventricular fibrillation after aortic declamping during cardiac surgery.

Ventricular fibrillation is common after aortic declamping during cardiac surgery, and the metabolic demands of such fibrillation, or its treatment by means of countershock, may contribute to myocardial injury. To determine the effects of administering intravenous lidocaine just before aortic declamping, we randomly divided 194 cardiac surgery patients into 2 groups. One hundred patients (group A) received lidocaine, 200 mg intravenously, 3 minutes before aortic declamping; and 94 patients (group B) received no medication before declamping. Multiple baseline variables, including clamp times, medications, electrolyte values, ventricular function, and the extent and type of surgery, were similar for both groups. After aortic declamping, 31 of the 100 patients in group A had ventricular fibrillation, as did 57 of the 94 patients in group B (p < 0.001). Of those who fibrillated, the group-A patients required a mean of 1.76 countershocks, whereas the group-B patients required a mean of 2.68 countershocks (p < 0.05). Serum potassium level also affected the incidence of ventricular fibrillation, independently of lidocaine. Elevated serum potassium levels were associated with a lower incidence of ventricular fibrillation. Although lidocaine was independently protective at all potassium levels, the combination of lidocaine and a high serum potassium level had the greatest effect in preventing fibrillation. In patients who had potassium levels higher than 5.1 mEq/l and who were also given lidocaine, the incidence of ventricular fibrillation was lower than 15%.

Echocardiographic and hemodynamic features of severe aortic regurgitation with diastolic opening of the aortic valve.

Severe aortic regurgitation may be associated with premature aortic valve opening. Several possible etiologies for this diastolic opening have been suggested. We present a patient with hemodynamic data, M-mode and 2-D echocardiography in the setting of severe aortic regurgitation and diastolic aortic valve opening. Our data lead us to conclude that aortic valve opening in this situation is neither from passive flotation nor dependent on atrial systole. We believe that active ventricular recoil mechanisms can facilitate increases in diastolic ventricular pressure which then can transiently exceed aortic pressure in the setting of severe aortic regurgitation. This hemodynamic observation suggests that the valve opening is an active process.

Steady-state evoked responses to sinusoidally amplitude-modulated sounds recorded in man.

Steady-state potentials evoked in response to binaural, sinusoidally amplitude-modulated (AM) pure tones and broadband noise signals were recorded differentially from position F4 and the ipsilateral mastoid on the human scalp. The responses elicited by the AM stimuli were approximately periodic waveforms whose energy was predominantly at the modulation frequency of the stimulus. The magnitude of responses was between 0.1 and 4 microV for modulation frequencies between 2 and 400 Hz imposed on a 1-kHz carrier signal. The magnitude of the responses increased linearly with log modulation depth for low (4 Hz) and high (80 Hz) modulation rates. The response magnitude also increased linearly with the mean intensity of the sound for intensities up to 60 dB above the subject's pure tone threshold; at higher levels the response saturated. The relationship between response magnitude and modulation frequency (the modulation transfer function) was a lowpass function for both pure tone and broadband noise carrier signals. The modulation transfer functions were similar to those obtained from human psychophysical measurements where spectral cues are either unavailable or not used by the subject. The responses also contained a significant component at the second harmonic of the modulation frequency. The magnitude of this component was greatest at modulation rates between 5 and 20 Hz. The responses elicited by ipsilateral and contralateral monaural stimulation were approximately equal in magnitude, and binaural stimulation produced a potential 30% greater than the individual monaural responses. It is suggested that the evoked response represents the entrained neural activity to temporal amplitude fluctuations, and reflects the psychophysically measured performance of the auditory system for the detection and analysis of amplitude modulation.

Delineation of FM rate channels in man by detectability of a three-component modulation waveform.

Adaptation studies have provided evidence for auditory mechanisms which operate on the modulation waveform of frequency-modulated sounds, and that these mechanisms behave like a series of channels selectively tuned to a limited range of modulation rates. In the present experiments, measurements of the modulation detectability threshold of a frequency-modulated tone, which had a modulation waveform spectrum consisting of three components: one component at the modulation rate and two sidebands which could be set to different frequency positions on either side of it, revealed that when the two sidebands were located within a limited bandwidth around the central component they contributed to the detection of the modulation. However, when the sidebands were more widely separated from the central component, the modulation detection threshold was dependent only on the magnitude of the central component. Within the area of sideband interaction, there was an inversely proportional relationship between the magnitude of the sidebands and the modulation threshold. Differences in the time-integrated sound spectra for the FM signals, although very complex, do not contain changes which adequately explain the data on the basis of critical band mechanisms, or a peak-to-peak detection model. The data provide further evidence in support of the hypothesis derived from adaptation studies that channels selectively sensitive to the rate of frequency modulation in frequency-modulated tones are concerned in the processing of frequency-modulated signals.

Pacemaker-induced pseudotricuspid regurgitation.

A patient with aortic stenosis and ventricular pacemaker had clinical findings suggesting tricuspid regurgitation. Her presentation was actually caused by regular and constant cannon waves resulting from ventriculoatrial conduction of paced beats. The correct diagnosis was confirmed by abolition of hepatic pulsations during atrial pacing at the time of cardiac catheterization. Therapy consisted of restoring antegrade atrioventricular conduction.

Unsuspected giant cell arteritis diagnosed at open heart surgery.

A 62-year-old patient undergoing aortocoronary bypass grafting had giant cell arteritis diagnosed by routine aortic biopsy done at the graft insertion site. This finding led to the tissue diagnosis of temporal arteritis and the institution of steroid therapy. In retrospect, vague symptoms of headache and fatigue, which had been attributed to side effects of antianginal therapy, were probably caused by giant cell arteritis. The population undergoing aortocoronary bypass grafting is in an age group at risk for giant cell arteritis. Routine aortic biopsy specimens should be carefully examined with this in mind.

Intestinal strongyloidiasis. A case report and review of the literature.

A patient infected with Strongyloides stercoralis presented with hematemesis and abdominal pain mimicking peptic ulcer disease. Radiologic evaluation, however, suggested Crohn's disease of the proximal small intestine. Aspiration of intestinal fluid and a small bowel biopsy lead to a diagnosis of invasive strongyloidiasis. This case is presented and the literature reviewed to demonstrate the protean manifestation of this parasite which commonly involves the gastrointestinal tract.