Biomedical subjects

H R Middlekauff

Publications and source records attributed to H R Middlekauff.

42 records · Page 3Linked to original sources

PubMed1992

Identifying sites for catheter ablation of ventricular tachycardia.

The approach to localizing sites for catheter ablation of ventricular tachycardia foci depends on the type of tachycardia. In large reentry circuits such as those arising from infarct scars, areas of slow conduction in and around the scar should be targeted. During sinus rhythm, these can be suspected from the presence of fractionated electrograms and, at some sites, long stimulus to QRS delays during pacing. Slow conduction areas can be classified as: 1. central slow conduction zone sites, 2. exits from the slow conduction zone, 3. entrances to the slow conduction zone, and 4. bystander areas which are not involved in the tachycardia circuit. In the central slow conduction zone stimulation entrains or resets tachycardia with a long stimulus to QRS (S-QRS) delay (40 to greater than 300 ms) without altering the QRS morphology (entrainment with concealed fusion). At slow conduction zone exits, presystolic electrograms are recorded during VT, the pacemap matches the VT QRS morphology, and with pacing during VT the S-QRS interval is relatively short and VT may or may not be entrained. At entrances to the slow conduction zone electrogram timing is variable but early diastolic electrograms are expected and the pace-map QRS may differ from the VT QRS morphology. Relatively late stimuli or slow trains of stimuli entrain VT with concealed fusion with a relatively longer S-QRS interval than observed in the central slow conduction zone. Early stimuli may entrain VT while altering the QRS morphology due to propagation of the stimulated antidromic wavefront out of the scar from a site other than the tachycardia exit. At bystander sites electrogram timing, pace-mapping, and the effects of programmed stimulation are variable but may occasionally mimic reentry circuit sites. Relatively late stimuli are likely to capture the site without altering the VT. If discrete electrograms are present, analysis of these during pacing may provide further evidence that the site is not in the reentry circuit. Catheter ablation will probably be most effective at central slow conduction zone sites. When VT originates from a small focus surrounded by normal myocardium, such as is likely for idiopathic RV outflow tract and some idiopathic left ventricular tachycardias, presystolic electrical activity and pacemapping are likely to identify the tachycardia focus. For macroreentry involving the bundle branches, the right bundle branch can be easily targeted.

Animals↗

PubMed1991

Prognostic significance of atrial fibrillation in advanced heart failure. A study of 390 patients.

BACKGROUND: Atrial fibrillation is common in advanced heart failure, but its prognostic significance is controversial. METHODS AND RESULTS: We evaluated the relation of atrial rhythm to overall survival and sudden death in 390 consecutive advanced heart failure patients. Etiology of heart failure was coronary artery disease in 177 patients (45%) and nonischemic cardiomyopathy or valvular heart disease in 213 patients (55%). Mean left ventricular ejection fraction was 0.19 +/- 0.07. Seventy-five patients (19%) had paroxysmal (26 patients) or chronic (49 patients) atrial fibrillation. Compared with patients with sinus rhythm, patients with atrial fibrillation did not differ in etiology of heart failure, mean pulmonary capillary wedge pressure on therapy, or embolic events but were more likely to be receiving warfarin and antiarrhythmic drugs and had a slightly higher left ventricular ejection fraction. After a mean follow-up of 236 +/- 303 days, 98 patients died: 56 (57%) died suddenly, and 36 (37%) died of progressive heart failure. Actuarial 1-year overall survival was 68%, and sudden death-free survival was 79%. Actuarial survival was significantly worse for atrial fibrillation than for sinus rhythm patients (52% versus 71%, p = 0.0013). Similarly, sudden death-free survival was significantly worse for atrial fibrillation than for sinus rhythm patients (69% versus 82%, p = 0.0013). By Cox proportional hazards model, pulmonary capillary wedge pressure on therapy, left ventricular ejection fraction, coronary artery disease, and atrial fibrillation were independent risk factors for total mortality and sudden death. For patients who had pulmonary capillary wedge pressure of less than 16 mm Hg on therapy, atrial fibrillation was associated with poorer 1-year survival (44% versus 83%, p = 0.00001); however, in the high pulmonary capillary wedge pressure group, atrial fibrillation did not confer an increased risk (58% versus 57%). CONCLUSIONS: Atrial fibrillation is a marker for increased risk of death, especially in heart failure patients who have lower filling pressures on vasodilator and diuretic therapy. Whether aggressive attempts to maintain sinus rhythm will reduce this risk is unknown.

Actuarial Analysis↗

PubMed1990

Comparison of frequency of late potentials in idiopathic dilated cardiomyopathy and ischemic cardiomyopathy with advanced congestive heart failure and their usefulness in predicting sudden death.

Signal-averaged electrocardiograms were obtained in 62 consecutive patients with advanced congestive heart failure (CHF) undergoing evaluation for possible heart transplantation to determine if late potentials: (1) provide unique information compared to assessment of ventricular ectopic activity on ambulatory electrocardiogram, and (2) identify a subgroup of CHF patients with higher sudden death risk. Patients with a history of cardiac arrest or sustained ventricular tachycardia were excluded. CHF was due to old myocardial infarction in 40 patients and idiopathic dilated cardiomyopathy in 22 patients. Late potentials were present in 16 of 40 (40%) patients with old infarction but in only 3 of 22 (14%) patients with nonischemic CHF (p = 0.03). Twenty-four-hour ambulatory electrocardiograms were obtained in 34 patients (55%). Total ventricular ectopic activity and repetitive forms of ectopy were similar in patients with and without late potentials. Nine patients died suddenly, 9 had nonsudden death, 15 underwent heart transplantation and 29 were alive and well after a mean follow-up of 218 +/- 154 days. At 1 year, the actuarial risk of death was 37% and of sudden death was 20%. Sudden death risk was 12% in patients with late potentials versus 21% in those without (p = 0.73). Thus, the incidence of the arrhythmia substrate producing late potentials depends on the CHF etiology. The signal-averaged electrocardiogram and ambulatory electrocardiogram provide independent information for possible risk assessment in CHF. However, late potentials are poor predictors of sudden death risk when CHF is advanced, possibly due to the heterogeneity of causes of sudden death--ventricular tachycardia being only 1 of many possible mechanisms.

Arrhythmias, Cardiac↗

PubMed1990

Linking: a mechanism of intermittent preexcitation in the Wolff-Parkinson-White syndrome.

Intermittent preexcitation in the Wolff-Parkinson-White syndrome has been equated with a long accessory pathway refractory period and long R-R interval between preexcited beats in atrial fibrillation and therefore a low risk for sudden death. A case of Wolff-Parkinson-White syndrome in which preexcitation became intermittent following procainamide infusion, with only moderate prolongation of the accessory pathway refractory period but marked prolongation of the shortest preexcited R-R interval in atrial fibrillation, is described. Programmed ventricular and atrial stimulation demonstrated that intermittent preexcitation was caused by concealed conduction producing a linking phenomenon, facilitated by the antiarrhythmic drug. Linking due to concealed retrograde penetration of a propagated impulse into the accessory pathway may contribute to the disparity between accessory pathway refractory period and shortest preexcited R-R interval in atrial fibrillation in some patients and may be a confounding factor in the interpretation of noninvasive tests of accessory pathway conduction.

Adolescent↗

PubMed1988

Clinical significance of a single test for anti-cardiolipin antibodies in patients with systemic lupus erythematosus.

PURPOSE: Clinicians have difficulty interpreting results of tests for anti-cardiolipin antibodies (aCL) because of conflicting reports of the clinical associations of these antibodies in patients with systemic lupus erythematosus (SLE). We therefore decided to evaluate the clinical associations of aCL in an effort to facilitate interpretation of single reports of either positive or negative test results. We also assessed the role of estrogen on the development of aCL. PATIENTS AND METHODS: The study population consisted of 85 consecutive outpatients with SLE and 40 control subjects. Serum samples and clinical and laboratory data were obtained from each patient and control. Testing for aCL was performed using a standardized enzyme-linked immunoabsorbent assay developed at an international workshop. RESULTS: The presence of aCL was documented in 42.4 percent of patients with SLE and 7.5 percent of control subjects. In patients with SLE, these antibodies were significantly associated with thrombosis, fetal loss, and thrombocytopenia, but not with other manifestations. Measurement of all isotypes optimized clinical correlations. Titers did not add clinical utility. Fluctuations of levels of aCL occurred, making it difficult to interpret a single negative result. Among control subjects, the presence of aCL was not significantly more common in women who used oral contraceptives. CONCLUSION: Our findings suggest that positive results of testing for aCL correlate with a predisposition for thrombosis, fetal loss, and thrombocytopenia in patients with SLE; however, the test is not predictive for other clinical manifestations of SLE, including activity and severity of disease. We believe that measurement of all isotypes of aCL should be performed in patients with SLE considering pregnancy, to identify those with a high risk of fetal loss, and in SLE patients with a thrombotic episode.

Adult↗

PubMed1987

Polyarteritis nodosa of the epididymis in a patient with Whipple's disease.

The case of a 55-year-old white male who developed necrotizing arteritis localized to the superior pole of the epididymis is presented. He had a history of Whipple's disease and euthyroid Graves' disease. Histopathologic section of an extratesticular mass showed a necrotizing vasculitis with giant cells; periodic acid Schiff stain for Whipple "bacilli" was negative. The combination of rare diseases in our patient suggests the possibility of a common infectious or immune etiology, perhaps mediated via circulating immune complexes.

Epididymis↗