Ethnic Comparison of Clinical Characteristics and Ischemic Stroke Subtypes Among Young Adult Patients With Stroke in Hawaii

BACKGROUND AND PURPOSE

Native Hawaiians and other Pacific Islanders (NHOPI) with ischemic stroke have younger age of stroke onset compared with whites. However, ethnic differences in stroke subtypes in this population have been inadequately studied.

METHODS

Consecutive young adult patients (aged ≤55 years) who were hospitalized for ischemic stroke between 2006 and 2012 at a tertiary center in Honolulu were studied. Clinical characteristics and stroke subtypes based on pathophysiological TOAST classification (Trial of Org 10172) of NHOPI and Asians were compared with whites.

RESULTS

A total of 427 consecutive young adult (mean age, 46.7±7.8 years) patients (NHOPI 45%, Asians 38%, and whites 17%) were studied. NHOPI had a higher prevalence of hypertension, diabetes mellitus, prosthetic valve, higher body mass index, hemoglobin A1c, and lower high-density lipoprotein than whites (all P<0.05). Stroke subtype distribution was not different between the ethnic groups. Specifically, the prevalence of small-vessel disease was similar between NHOPI (26.6%), whites (28.4%), and Asians (24.8%). In the univariate analyses, the use of intravenous tissue-type plasminogen activator was lower among NHOPI (4.7%; P=0.01) and Asians (3.1%; P=0.002) than among whites (12.5%). In the multivariable model, NHOPI (odds ratio, 0.35; 95% confidence interval, 0.12-0.98) and Asians (odds ratio, 0.23; 95% confidence interval, 0.07-0.74) were less likely to be treated with intravenous tissue-type plasminogen activator than whites.

CONCLUSIONS

NHOPI have greater cardiovascular risk factors than whites, but there were no differences in stroke subtypes between the ethnic groups. Furthermore, NHOPI and Asians may be less likely to be treated with intravenous tissue-type plasminogen activator than whites.

Abstract WP172: Ethnic Disparities in the Use of Tissue Plasminogen Activator Among Young Adult Stroke Patients in Hawaii

Introduction: Minorities with ischemic strokes are younger and less likely to receive intravenous tissue plasminogen activator (IV tPA) compared to whites; However, disparities in the use of IV tPA in the multi-ethnic population of Hawaii have not been adequately studied.

Hypothesis: Native Hawaiians and other Pacific Islanders (NHOPI) and Asians who are hospitalized with ischemic stroke receive less IV tPA compared to whites.

Methods: We conducted a retrospective study on consecutive young adult patients (age ≤55) hospitalized for ischemic stroke at a single tertiary center on Oahu between 2006 and 2012. Clinical characteristics and the use of IV tPA among NHOPI and Asians were compared to whites. Patients without race/ethnicity data (n=28) and postoperative strokes (n=22) were excluded.

Results: A total of 462 consecutive young adult (mean age 47±9 years) ischemic stroke patients (whites 16%, Asians 36%, NHOPI 43%, Other 5%) were studied. NHOPI had higher prevalence of hypertension (NHOPI 75% vs. whites 49%, p<0.0001), diabetes (NHOPI 46% vs. whites 22%, p=0.0003), higher body mass index (NHOPI 33±9 cm/m2 vs. whites 28±7 cm/m2, p<0.0001), and hemoglobin A1c (NHOPI 8.9 ± 2.9% vs. whites 7.2 ± 2.5%, p=0.002) compared to whites. Clinical characteristics were similar between Asians and whites. The use of IV tPA was lower among NHOPI (4.6%, p=0.01) and Asians (3.0%, p=0.002) compared to whites (13.2%).

Conclusions: NHOPI represented the major ethnic group among the young adult stroke population in Hawaii and had higher instances of hypertension and diabetes compared to whites. NHOPI and Asians both had significantly lower rates of IV tPA use compared to whites. Further study is needed to assess the barriers associated with the use of IV tPA among these minority groups.

Hypertension following arterial baroreceptor denervation in the unanesthetized dog

Studies were conducted on unanesthetized dogs (1) in the control state, (2) after carotid sinus denervation plus section of the cervical aortic nerves (SCAD), and (3) after carotid sinus denervation plus section of intrathoracic vegal branches which innervate arterial and cardiopulmonary baroreceptors, the heart, lungs, and other structures (STD). Mean values and standard deviations of blood pressure and heart rate were measured during many 75-minute recording sessions. The control mean arterial pressure was 94.8 +/- 8.9 mm Hg. The mean pressure after SCAD was 105.5 +/- 9.5 mm Hg, 10.0 mm Hg higher (P less than 0.05) than in the control state, whereas after STD, the mean pressure was 119.5 +/- 16.8 mm Hg, 25.3 mm Hg higher (P less than 0.001) than in the control state. The standard deviation of pressure was increased (P less than 0.01) by either denervation procedure. The mean pressure after STD was higher than after SCAD (P less than 0.05). Ten of 12 animals with SCAD showed residual baroreceptor reflexes (seven from intrathoracic receptors) whereas, after STD, six of 11 animals showed reflexes (one from intrathoracic receptors). SCAD only occasionally produces denervation as complete as that produced by STD. A larger increase in arterial pressure follows a more complete denervation of vagally innervated baroreceptors. We believe that our procedures do not denervate all arterial baroreceptors. Chronic denervation of arterial baroreceptors leads to a widely varying, elevated arterial pressure. The increase in pressure has persisted more than 1 1/2 years.

Hypertension following denervation of aortic baroreceptors in unanesthetized dogs

After cervical aortic nerve section, mean arterial pressure in the unanesthetized dog increased by an average of 7.4 mm Hg. Following a more extensive denervation of aortic arch receptors by section of intrathoracic vagal branches, arterial pressure increased by 16.7 mm Hg. The above changes were seen in the stable state after the effects of surgery had disappeared. In both cases carotid baroreceptors were functional. After administration of nitroglycerin and phenylephrine subsequent to either denervation procedure, blood pressure changes were larger and heart rate responses were smaller than in the control state. The unanesthetized dog regulates mean arterial pressure at a higher-than-normal pressure after aortic baroreceptor denervation. Reflexes from the aortic baroreceptors continuously participate in the normal control of mean arterial pressure. Section of the cervical aortic nerves only partially denervates aortic baroreceptors. Our findings may be relevant to human essential hypertension.

Arterial baroreceptor fibers from the aortic region of the dog in the cervical vagus nerve

The neural pathways followed by sensory fibers from arterial baroreceptors in the aortic region of the dog were investigated with neurophysiological recording. Systemic arterial baroreceptor fibers separate from the depressor nerve were found in the left cervical vagus in each of five dogs investigated; at most two fibers were isolated from each dog due to the difficulty of the dissection. These fibers originated from or above the aortic arch region. One baroreceptor fiber had its arterial sensory ending below the fifth rib. In the right cervical vagus in six dogs, visual evidence of fiber activity from systemic arterial baroreceptors could not be produced; only subjective (auditory) evidence for the presence of systemic arterial baroreceptor fibers was obtained. The number of these arterial baroreceptor fibers, which run in the vagus nerve but are not part of the depressor nerve, appeared to be smaller than the number of arterial baroreceptor fibers in the depressor nerve.

Effect of dipyridamole on microaggregate formation in the pump oxygenator

Images