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Biomedical subjects

R Krishnan

Publications and source records attributed to R Krishnan.

139 records · Page 8Linked to original sources
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Potential added value of three-dimensional reconstruction and display of single photon emission computed tomographic gated blood pool images.

BACKGROUND: Single photon emission computed tomographic (SPECT) acquisition provides potential advantages for blood pool imaging. However, the method has been little applied. METHODS: An improved method of three-dimensional (3-D) reconstruction and display of SPECT equilibrium blood pool scintigrams and related phase data was developed. Dynamic slices and volume-rendered dynamic 3-D images were displayed. Images were viewed from each of 34 solid angles referenced to a sphere surrounding the reconstruction field. Each image pixel was "painted" with intensity-coded regional amplitude and color-coded for its phase angle. The method was applied to evaluate the cardiac anatomy, regional contraction, and related conduction sequence at rest in 17 patients. Twelve had normal left ventricular function including 7 patients with minimal septal preexcitation. Five patients had abnormal left ventricular function, including 2 with left bundle branch block. RESULTS: Slices contained all of the functional information, but necessary data integration was time-consuming and evaluation of chamber size and anatomy was difficult. Three-dimensional projection images condensed and integrated the data, presenting new vantage points on anatomy, contraction, and conduction not otherwise available in the clinically limited angulations of planar images. This provided excellent visual separation of cardiac chambers with full and increased visualization of right and left ventricular wall motion in all segments compared with the conventional projections acquired clinically (p < 0.05). Atria and great vessels were well separated with evident size and function. Phase-angle progression paralleled the electrocardiogram, permitting bypass pathway localization and the direct noninvasive localization of posteroseptal pathways. CONCLUSIONS: The 3-D method permits greater access to and utilization of SPECT blood pool image data. It suggests specific advantages for clinical use.

Adult↗
PubMedDate not supplied

Anxiety and vagal control of heart rate.

OBJECTIVE: Prospective studies have demonstrated that anxiety predicts sudden cardiac death, but the mechanism underlying this increased risk is unclear. This study examined whether anxiety is associated with reductions in vagal control of heart rate in healthy volunteers. METHOD: Trait anxiety (T-ANX) was measured, using the Spielberger State-Trait Anxiety Inventory (STAI), in 93 healthy men and women 25 to 44 years of age. Power spectral analysis was used to measure two indices of vagal control: baroreflex control of heart rate (BRC) and respiratory sinus arrhythmia (RSA). RESULTS: High trait anxiety (T-ANX > 41, N = 23) was associated with significantly reduced vagal control of the heart, compared with low trait anxiety (T-ANX < 31, N = 22), as indicated by a 36% reduction in BRC (p< .001) and an 8% reduction in RSA (p<.05). Furthermore, T-ANX scores were negatively correlated with levels of BRC (r = -.30, p<.005), and levels of RSA (r = -.26, p <.05). CONCLUSIONS: These findings provide evidence that trait anxiety is associated with reductions in vagal control of the heart. Additional studies are needed to examine whether low vagal control is involved in the increased risk of sudden cardiac death associated with anxiety.

Adult↗
PubMedDate not supplied

Anxiety reduces baroreflex cardiac control in older adults with major depression.

OBJECTIVE: Although depression and anxiety predict risk of cardiac mortality, the contributions of depression and anxiety to vagal cardiac control have not been systematically evaluated. The goal of this study was to examine the relationship between state anxiety and vagal control of heart rate in older adults with major depressive disorder (MDD). Older adults (50-70 years old) were selected for this study because of the greater cardiac risk associated with low vagal cardiac control across this age range. METHODS: Fifty-six men and women with MDD were evaluated. MDD was diagnosed using the Diagnostic Interview Schedule, and severity of depression was measured using the Beck Depression Inventory and the Hamilton Rating Scale for depression. State anxiety was measured using the Spielberger State Anxiety Inventory. Power spectral analysis was used to measure two indices of vagal control: baroreflex control of heart rate (BRC(SPEC)) and respiratory sinus arrhythmia (RSA). RESULTS: State anxiety was negatively correlated with levels of BRC(SPEC) (r = -0.32, p < .05), whereas depression severity was not related to either RSA or BRC(SPEC). Furthermore, BRC(SPEC) was reduced by approximately 33% in MDD patients with state anxiety scores (ST-ANX) in the highest quartile (ST-ANX > 41, N = 13), compared with patients with ST-ANX scores in the lowest quartile (ST-ANX < 25, N = 14; p < .05). CONCLUSIONS: Anxiety, but not depression severity, is associated with reduced BRC(SPEC) in older men and women. Future studies are needed to determine whether comorbid anxiety contributes to the increased cardiovascular risk associated with MDD.

Aged↗
PubMedDate not supplied

Complete axillary conversion after neoadjuvant chemotherapy in locally advanced breast cancer: a step towards conserving axilla?

OBJECTIVES: This study was designed to assess the clinical, sonographic and histopathological response of axillary lymph node metastasis to neoadjuvant chemotherapy in patients with locally advanced breast cancer. MATERIAL AND METHODS: Forty patients with locally advanced breast cancer (LABC) with clinically palpable or sonographically detectable axillary nodes were studied. FNAC of the primary tumor and axillary nodes was done and patients were started on neoadjuvant chemotherapy. Axillary nodes were assessed clinically and sonographically for response after 3 cycles of chemotherapy. All patients underwent total mastectomy with axillary clearance and the lymph nodes in the specimen were examined for metastasis. RESULTS: 47% patients had complete clinical nodal response, while 19% showed complete sonographic response. Complete pathological nodal response was documented in 22% of patients. Ultrasonography was found to be more sensitive than clinical examination in assessing complete nodal response. 10% of the patients had complete pathological response of both primary tumor and axillary nodes. There was significant correlation between pathological response of primary tumor and lymph nodes (P=0.004). Patients with complete sonographic or clinical response were found to have no or minimal residual disease in axilla and hence axillary dissection may be avoided in them.

Analysis of Variance↗
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Effect of anti-Helicobacter pylori therapy on outcome of iron-deficiency anemia: a randomized, controlled study.

BACKGROUND: Helicobacter pylori infection may play a role in iron-deficiency anemia. METHODS: In 52 patients with iron-deficiency anemia, H. pylori status was determined using rapid urease test and histology. H. pylori -positive patients were randomly assigned to receive anti- H. pylori treatment either immediately (Group I) or after a delay of one month (Group II); in addition, all patients received oral ferrous sulfate for three months. Patients testing negative for H. pylori (Group III) received only oral ferrous sulfate. Hematological parameters were tested every month. RESULTS: Of 52 patients, 32 (61.5%) had H. pylori infection. At the end of one month, median increase in hemoglobin level was lower in Group II than in Groups I and III (1.1 g/dL vs. 3.6 g/dL and 1.9 g/dL, respectively; p=0.025), as were that in serum iron (19 mcg/dL vs. 55.5 mcg/dL and 41 mcg/dL; p=0.019). During the second month, after H. pylori infection in Group II had been treated, median increase in hemoglobin in this group was comparable to those in Groups I and III (3.7 g/dL vs. 2.5 g/dL and 2.5 g/dL. CONCLUSION: In patients with iron-deficiency anemia, presence of H. pylori infection is associated with a poorer response to oral iron therapy, which improves with treatment for H. pylori infection.

Anemia, Iron-Deficiency↗