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Donald L King

Publications and source records attributed to Donald L King.

10 recordsLinked to original sources
PubMed2005

Left heart failure with a normal ejection fraction: identification of different pathophysiologic mechanisms.

BACKGROUND: Although heart failure with a normal ejection fraction (HFNEF) is a clinically heterogeneous syndrome, a single pathophysiologic mechanism, diastolic dysfunction, is often ascribed to explain this condition. In view of the clinical heterogeneity of these patients, we hypothesized that subgroups of HFNEF patients may have different underlying pathophysiologic mechanisms. METHODS AND RESULTS: Freehand 3-dimensional echocardiography was used to measure left ventricular end-systolic and end-diastolic volumes in 99 asymptomatic normal controls and 2 groups with chronic heart failure: 35 patients with normal ejection fraction with longstanding hypertension (hypertensive HFNEF) and 11 patients with hypertrophic cardiomyopathy without a history of hypertension (nonhypertensive HFNEF). These data, combined with cuff sphygmomanometry and Doppler estimates of LV end-diastolic pressure (EDP) yielded estimated pressure-volume loops and slope (E es,sb ) of the end-systolic pressure-volume relationship, a load independent index of chamber contractility. Nonhypertensive HFNEF patients required high EDPs (21 +/- 2 versus 15 +/- 3 mm Hg in normals, P < .0001) to achieve normal EDVs (98 +/- 25 versus 95 +/- 21 mL in normals, P = NS). Although systolic function (E es,sb ) did not differ from normal, systolic blood pressure was lower than normal in these patients (114 +/- 10 versus 124 +/- 14 mm Hg in normals, P < .05). Hypertensive HFNEF patients also had increased EDP (20 +/- 2 mm Hg), but this was observed at higher than normal EDVs (118 +/- 29 mL, P < .05). Among patients with hypertensive HFNEF, 2 subgroups emerged, 1 with a high E es,sb (4.23 +/- 0.54 versus 2.1 +/- 0.7 mm Hg/mL) and 1 with normal E es,sb (2.31 +/- 0.51 mm Hg/mL). The former group was composed of elderly women with small body size (body surface area 1.7 +/- 0.2 versus 1.9 +/- 0.2 m 2 , P = .02) who had concentrically remodeled ventricles and low stroke volumes. The latter group was more diverse in age, body size, and included patients of both genders with increases in ventricular volumes, stroke volume, and mass consistent with a volume overload state. CONCLUSION: Although HFNEF is commonly thought of as being the result of a single hemodynamic mechanism, these data indicate that subgroups exist with distinctly different underlying pathophysiologies.

Age Factors↗
PubMed2005

Ventricular volume and length in hypertensive diastolic heart failure.

BACKGROUND: Patients with diastolic heart failure are thought to have a normal or small ventricle with impaired ventricular filling that requires increased filling pressure to maintain normal stroke volume. In this study we test the hypothesis that patients with hypertensive diastolic heart failure have increased left ventricular volumes compared with age-, sex-, and body size-matched control subjects. METHOD: Left ventricular chordal dimensions from 2-dimensional echocardiography and volumes from 3-dimensional echocardiography were obtained in control subjects (n = 96) and patients with hypertensive diastolic heart failure (n = 28) and compared before and after controlling for age, sex, and body size. RESULTS: Volumes by 3-dimensional echocardiography were significantly larger in the heart failure group than in the control group (P < .05). After matching for age, sex, and body size, volumes remained significantly larger in the patients with heart failure (P < .05). Chordal dimensions were not significantly different between the two groups. Stroke volume and centerline length of the ventricle were significantly increased in the heart failure group compared with matched control subjects (P < .05). CONCLUSIONS: Our group of patients with hypertensive diastolic heart failure had significantly increased left ventricular volumes and stroke volume compared with control subjects, compatible with volume overload heart failure. Two-dimensional echocardiographic measurement of the ventricular chordal dimension failed to detect this enlargement. Ventricular length appeared to be preferentially increased in the patients with hypertensive diastolic heart failure.

Aged↗
PubMed2005

Discrimination is more closely associated with perceived similarity than with distance and color.

Diverse factors affect perceived similarity and discrimination, with high perceived similarity associated with poor discrimination. To investigate this hypothesis, college students made speeded same-different discriminations between 2 achromatic colors when they were contiguous and separated, did the same with 2 chromatic colors, and rated similarity. Compared with chromatic color, the separation for achromatic color impaired the performance on different stimuli more than on same stimuli with response bias controlled, which implied an increase in the perceived similarity of the discriminated stimuli, hurt overall performance, and elevated rated similarity. Thus, discrimination was more closely associated with 2 measures of perceived similarity than with distance and color, in support of the hypothesis.

Color Perception↗
PubMed2002

Myocardial contraction fraction: a volumetric index of myocardial shortening by freehand three-dimensional echocardiography.

OBJECTIVES: This study sought to evaluate myocardial contraction fraction (MCF) as an index of myocardial shortening by comparison to conventional shortening indices in patients with hypertensive hypertrophy, athletes with physiologic hypertrophy and sedentary normal adult subjects. BACKGROUND: A significant percentage of patients with hypertensive hypertrophy have "normal" or "preserved" left ventricular (LV) systolic function by conventional echocardiographic measures whereas their systolic function is depressed when measured by the two-dimensional echocardiographic mid-wall shortening fraction (MWSF). A three-dimensional echocardiographic measure of myocardial shortening analogous to MWSF has been lacking. We describe a volumetric measure of myocardial shortening, the MCF, as the ratio of stroke volume (SV) to myocardial volume (MV), and hypothesize that it may be useful to compare myocardial performance in patients with different degrees and types of hypertrophy. METHODS: We compared the MCF using freehand three-dimensional echocardiographic reconstruction of the LV to conventional measures of LV function (ejection fraction [EF], endocardial shortening fraction [SF] and MWSF) in subjects with pathologic hypertensive hypertrophy, heart failure symptoms and preserved EF (n = 17), athletes with physiologic hypertrophy (n = 41) and normal sedentary adults (n = 80). RESULTS: The EF was in the normal range for all three groups. The MCF was lower in hypertensive hypertrophy compared with normal subjects (0.33 +/- 0.05 vs. 0.44 +/- 0.07, p < 0.01). It also successfully differentiated physiologic hypertrophy from normal subjects (0.50 +/- 0.05 vs. 0.44 +/- 0.07, p < 0.01). The endocardial SF did not distinguish athletes from normal subjects and the MWSF did not distinguish hypertensive from physiologic hypertrophy. CONCLUSIONS: The MCF, a volumetric measure of myocardial shortening, demonstrates that myocardial shortening is decreased in hypertensive hypertrophy and increased in physiologic hypertrophy. The MCF may be useful in assessing differences in myocardial performance in patients with similar degrees of hypertrophy.

Adult↗
PubMed2002

Errors as a result of metal in the near environment when using an electromagnetic locator with freehand three-dimensional echocardiography.

BACKGROUND: Quantitative ventriculography by freehand 3-dimensional (3D) echocardiography with an acoustic spatial locator has been proven to provide highly accurate reproducible measurements of left ventricular volume, mass, and function. It has been shown to be 2 to 3 times better than conventional 2-dimensional echocardiographic techniques. Although accurate, the acoustic spatial locator uses a spark gap to generate hypersound for locating and is somewhat bulky. The Bird direct current electromagnetic locator (Ascension Technology Corp, Burlington, Vt) is a notable alternative locator for the freehand 3D system because it is small and easily portable. However, conductive metals in the near environment may adversely affect electromagnetic locator accuracy. To determine the feasibility of using the electromagnetic locator in a freehand 3D echocardiographic system in the conventional hospital environment, a series of experiments was carried out assessing the accuracy of such a system under various conditions of exposure to conductive metal. METHODS: Using tissue equivalent ellipsoid phantoms of known volumes, we compared volume measurement accuracy of the freehand 3D echocardiographic system equipped with the standard Bird or miniBird electromagnetic locator systems with our freehand acoustic spatial locator 3D echocardiographic system in 3 experiments: (experiment 1) no metal within 30 in (76.2 cm) of the phantoms and electromagnetic locator; (experiment 2) phantoms placed on a standard metal hospital stretcher with conductive metal less than 10 in (25.4 cm) from the phantoms and electromagnetic locator and with the echocardiographic machine greater than 30 in (76.2 cm) from the electromagnetic locator; and (experiment 3) phantoms placed on the same stretcher with conductive metal less than 10 in (25.4 cm) from the phantoms and electromagnetic locator and with the echocardiographic machine in its usual position approximately 10 in (25.4 cm) from the electromagnetic locator. RESULTS: For experiment 1 there was no significant volume error (<1%) by any system; no significant difference among the 3 locator systems (acoustic, Bird, or miniBird). For experiment 2 there was significant volume underestimation error by both electromagnetic locator systems (-10.9%, P <.05). For experiment 3 there was significant and greater volume underestimation error by both electromagnetic locator systems (-14.7%, P <.05) in close proximity to the echocardiographic machine. Interobserver variability was 5.1%. CONCLUSION: For quantitative ventriculography by a freehand 3D echocardiographic system, electromagnetic locator systems should not be used if conductive metal is in the near environment (<30 in [76.2 cm] from the locator). Accurate quantitative ventriculography may be performed with an electromagnetic locator system if the near environment is free of conductive metals.

Echocardiography, Three-Dimensional↗
PubMed2002

Noncompressibility of myocardium during systole with freehand three-dimensional echocardiography.

BACKGROUND: Measures of ventricular performance, such as the ejection fraction, assume that myocardium is noncompressible and does not change volume significantly from end diastole to end systole. Although this principle is widely accepted as true, little data exist in the literature to support it. Freehand 3-dimensional (3D) echocardiography has previously been shown to be highly accurate for measurement of myocardial mass and volume. Therefore, we hypothesized that it has sufficient accuracy to test the validity of this assumption. We measured myocardial volume at end diastole and end systole in 2 groups of subjects with hypertrophy. METHODS: Forty-one healthy young adult athletes and 17 adult patients with hypertension, hypertrophy, normal ejection fraction, and heart failure symptoms underwent examination with freehand 3D echocardiography. Endocardial and epicardial surfaces at end diastole and end systole were reconstructed, and their volumes were computed. From these surface volumes, myocardial volume at end diastole and end systole and epicardial stroke volume and endocardial stroke volume were calculated. These volumes were compared with the 2 sample paired t test. RESULTS: Myocardial volume was constant from diastole to systole (174.7 +/- 45.3 mL versus 174.6 +/- 45.8 mL; P = not significant), and endocardial and epicardial stroke volumes were identical (76.0 +/- 17.4 mL versus 76.0 +/- 17.1 mL; P = not significant). The average absolute difference between the end-diastolic and end-systolic myocardial volumes was 1.9 mL, or less than 1.1% of end-diastolic volume. CONCLUSION: Myocardial volume measured with freehand 3D echocardiography does not change significantly during systole. Myocardial volume may be considered noncompressible for purposes of measurement of ventricular function with freehand 3D echocardiography. Comparison of end-diastolic and end-systolic myocardial volumes may be used for quality assurance in performing 3D reconstructions.

Adult↗
PubMed2002

A brief delay decreases perceived similarity and improves discrimination.

A same-different discrimination between the colors of 2 halves of a circle was poorer when the halves were viewed simultaneously than when the delay between viewing them was 33 ms. The simultaneous discrimination also produced a poor performance on different stimuli relative to same stimuli in comparison to the successive discrimination. Poor-on-different performance should indicate high perceived similarity. The simultaneous colors were also judged as more similar. The delay did not alter the physical similarity of the colors. Thus, the delay may have decreased assimilation (perceived similarity) and thereby improved discrimination, in support of the hypothesis that perceived similarity frequently affects discrimination.

Color Perception↗
PubMed2002

The length of the retention interval, forgetting, and subjective similarity.

A long retention interval tends to result in the poor retention known as forgetting. A high subjective similarity between stimuli frequently produces their poor retention. Thus, a long retention interval may increase the subjective similarity between stimuli (the RIISS hypothesis), and this increase may produce forgetting. To examine this hypothesis, college students made speeded same-different discriminations between two lines or tones of different lengths or frequencies that were 400 ms or 3,300 ms apart, and they rated the similarity of these stimuli. The long interval produced poorer overall performance as expected, but also produced poorer performance on different than same stimuli, implying that it increased the subjective similarity between the initial and subsequent stimuli, and it also increased rated similarity, in support of the RIISS hypothesis. The position that stored stimuli lose less common information than distinctive information explains RIISS evidence better than does perturbation theory.

Attention↗
PubMedDate not supplied

A clinical algorithm to differentiate heart failure with a normal ejection fraction by pathophysiologic mechanism.

The incidence and prevalence of heart failure are increasing as the population ages. Epidemiologic studies demonstrate that more than half of heart failure patients have a normal ejection fraction. The pathophysiology of this disorder is not completely understood. It is primarily attributed to left ventricular diastolic dysfunction (a leftward- and upward-shifted end-diastolic pressure-volume relation), where left ventricular diastolic chamber size is normal or reduced despite greater-than-normal filling pressures, resulting in reduced stroke volume and cardiac output. Using classic measures derived from pressure-volume analysis, we delineate other possible combinations of the end-systolic and end-diastolic pressure-volume relation, and hence possible pathophysiologic mechanisms that could underlie the syndrome of heart failure with normal ejection fraction. We propose an algorithm for identifying the primary pathophysiologic mechanism of heart failure in the setting of a normal ejection fraction using three simple factors: blood pressure, electrocardiographic/echocardiographic evidence of left ventricular hypertrophy, and left ventricular size. The application of this algorithm may aid in guiding management and targeting much-needed therapies for this population.

Aged↗