Changes In Regional Function Research Articles

Impact of regional ventricular function, geometry, and dobutamine stress on quantitative 99mTc-sestamibi defect size.

Serial myocardial perfusion imaging with 99mTc-sestamibi (MIBI) was used to evaluate infarct risk area and salvage after thrombolysis. The purpose of this investigation was to determine whether changes in MIBI defect size observed after reperfusion may result in part from distortion of regional and global left ventricular geometry. Twenty-five open-chest dogs were subjected to either 15 minutes (groups 1A and 1B) or 3 hours (group 2) of left anterior descending coronary artery occlusion followed by 3 hours of reperfusion. MIBI was injected before occlusion (group 1A) or during occlusion (groups 1B and 2), and serial ECG-gated planar imaging was performed. Dobutamine was infused after 3 hours of reperfusion (groups 1B and 2) to transiently alter left ventricular size and function. Perfusion defect magnitude (DM) and extent (DE) were serially quantified with circumferential profile analysis of end-systolic (ES), end-diastolic (ED), and summed images. Flow was assessed with radiolabeled microspheres and correlated with myocardial MIBI activity. Myocardial thickening was assessed in the risk area with sonomicrometers. In group 1A dogs, ischemic dyskinesis produced large artifactual quantitative MIBI defects on ES images (DM, 9.3 +/- 1.3; DE, 27.8 +/- 6.0) that were significantly smaller on ED images (DM, 4.5 +/- 0.9, P < .05; DE, 4.4 +/- 2.3, P < .05). In addition, DM and DE correlated inversely with myocardial thickening on ES images (DM, r = -.84; DE, r = -.78) and summed images (DM, r = -.72; DE, r = -.61) but not ED images (DM, r = -.12; DE, r = -.15). An index of defect reduction derived from summed images correlated well with thickening fraction in stunned dogs (group 1B, r = .89) but poorly in infarcted dogs (group 2, r = .41) subjected to dobutamine stress. 99mTc-MIBI defect size may be affected by alteration of left ventricular geometry. Changes in regional function may confound analysis of risk area and myocardial salvage with serial 99mTc-MIBI imaging and may also affect defect size during pharmacological stress with dobutamine. Dobutamine 99mTc-MIBI imaging may be useful for distinguishing viable and nonviable myocardium.

The utility of SPECT lung perfusion scans in minimizing and assessing the physiologic consequences of thoracic irradiation

Purpose : Three-dimensional single photon emission computed tomography lung perfusion scans (SPECT) provide a unique quantitative 3-dimensional map of the distribution of functioning pulmonary vascular/alveolar subunits, information not provided by other imaging modalities. This report describes our initial experience utilizing these scans to assist in the design of radiation treatment beams and to assess changes in regional lung function following irradiation. Methods and Materials : Patients were immobilized and scanned in the treatment position with appropriate fuducial markers. Four millicuries of technetium 99M microaggregated albumin were injected and SPECT images of the lung were generated. Pre-treatment SPECT images were used to help design radiation beams to minimize irradiation of functioning lung. Pre- and post-treatment scans were compared to assess changes in regional function. These changes in function were then correlated with the regional radiation dose. Results : Pre-radiotherapy SPECT scans were obtained in 18 patients (11 with lung cancer). Marked variations in regional function were frequently noted. In patients with primary lung tumors, these variations were not necessarily immediately adjacent to the tumor volume. In general, patients with poor pulmonary function pre-treatment, in whom one would like to spare as much normal lung as possible, had the most non-uniform distribution throughout the lung of functioning vascular/alveolar subunits. In these cases, pre-treatment scans were most useful in designing radiation portals to minimize irradiation of functioning lung. SPECT scans were also used to detect changes in regional lung function secondary to radiotherapy in four patients. With doses in excess of 40 Gy, reductions in regional function were noted 1–6 months following completion of radiotherapy. These reductions were not necessarily accompanied by reductions in conventional pulmonary function tests, which are assessments of whole lung function and may not reflect regional lung injury if the volume affected is small. Conclusions : SPECT lung scans provide an excellent means of assessing regional lung function, superior to that obtainable with planar images. The functional data provided by the SPECT images is useful in designing “optimal” radiation treatment beams and in assessing the effect of radiotherapy on regional lung functions. Efforts are continuing in our laboratory to develop a dose response curve for regional lung damage using the tools of SPECT scanning and 3-dimensional dose calculations.

Myocardial stunning in dogs: Preconditioning effect and influence of coronary collateral flow

In open-chest dogs the left anterior descending (LAD) coronary artery diagonal branch was encircled with a pneumatic occluder. Pairs of ultrasonic crystals were inserted into LAD myocardium and remote normal muscle. The coronary artery was occluded for 5 minutes, followed by 10 minutes of reperfusion. This occlusion-reperfusion cycle was repeated 12 times, and after a final 90-minute reperfusion period the hearts were removed and stained with triphenyltetrazolium chloride. No heart had evidence of necrosis. Baseline shortening normalized for end-diastolic length averaged 10.4 ± 1.0% in the LAD area and 7.4 ± 0.8% in the remote normal myocardium. When analyzed as a percentage of baseline, segment shortening in the normal myocardium was not significantly altered by LAD occlusion and reperfusion. In contrast, during occlusions the LAD myocardium paradoxically lengthened. With the initial reperfusion, shortening was significantly depressed to 28.6 ± 8.6% of baseline. Although with subsequent reperfusions the return of function progressively decreased, the rate of deterioration was markedly attenuated after the first occlusion. By the end of the protocol many LAD segments lengthened paradoxically even after reperfusion, but in five hearts in which active contraction was preserved there was no significant change in regional function after the third cycle, suggesting a protective or preconditioning effect of earlier ischemia. There was a moderately good correlation between collateral blood flow and the degree of dysfunction following the initial 10-minute reperfusion ( r = −0.73). This correlation deteriorated during subsequent reperfusion periods, implying the collateral blood flow can be a predictor of the extent of myocardial stunning only after the initial one or two reperfusion cycles. Thereafter other as yet unidentified factors make baseline collateral flow unimportant.

An accurate, nontraumatic ultrasonic method to monitor myocardial wall thickening in patients undergoing cardiac surgery

Measurement of systolic wall thickening by sonomicrometry provides an accurate index of regional left ventricular function, but the trauma of crystal insertion limits its widespread clinical use. The first clinical application of a 10 MHz ultrasonic Doppler probe that can be either sutured or applied by suction to the epicardium and can measure wall thickening at any depth of the left ventricular wall is described. In 18 dogs, measurements obtained with the suction probe correlated well (r = 0.97) with those of a previously validated sutured probe.To assess clinical feasibility, the probe was applied to the epicardium of patients undergoing coronary bypass surgery. Good quality wall thickening signals were obtained with no complications. Transmural left ventricular thickening fraction before bypass surgery was 34 ± 3% (mean value ± SE) at the mid-ventricular lateral wall, 33 ± 4% at the anterior basal wall and 26 ± 4% at the mid-ventricular posterior wall. Right ventricular thickening fraction averaged 25 ± 3%. Endocardial thickening fraction tended to exceed epicardial thickening fraction, although the difference attained statistical significance (p < 0.05) only at the anterior basal wall.On average, thickening fraction during the immediate postoperative period remained unchanged compared with the preoperutive values, but a marked individual variability was observed, with 7 of 15 patients exhibiting a decrease and 8 an increase. Exteriorization of the wires attached to the sutured probe allowed continuous in situ monitoring of wall thickening in the postoperative period and subsequent removal of the probe, in six patients the crystal was left in place for 48 to 72 h after surgery and then removed without complications; good wall thickening signals were obtained for the entire period during which the probe was implanted.Thus, the Doppler probe is an accurate, atraumatic method for measuring right and left ventricular regional function. Transmural, endocardial and epicardial function can be mapped at various sites during surgery, and postoperatively one can monitor serial changes of regional function and assess the effects of cardioplegia and other therapeutic interventions. This technique should be useful for both investigative and clinical purposes.

Quantitative analysis of regional systolic function with left ventricular aneurysm.

Left ventricular aneurysm (LVA) remains a poorly understood entity, often resulting in congestive failure that is not consistently improved by standard resection with linear closure. Although other surgical approaches have been proposed, current methods to assess their effect on left ventricular function are not adequate. The purpose of the present study was to quantitatively define regional systolic function in patients with LVA and to assess acute changes in regional function after standard repair. Seven patients underwent resection of an anteroapical LVA. Intraoperative two-dimensional echocardiography was performed off cardiopulmonary bypass immediately before and after resection. In all patients, short-axis views at the papillary muscle (apex) level showed anteroseptal paradox and distorted geometry, whereas at the mitral valve (base), symmetric wall motion and geometry were preserved. Videotaped echo images were divided into octants by a floating axis fitted to internal landmarks. Myocardial area and midwall perimeter were obtained for each octant, and wall thickness was calculated at end diastole (ED), isovolumetric systole (IS), and end systole (ES). Wall thickening (delta t) for each segment was calculated as the percent increase in thickness from ED and averaged for all seven patients. At the apex level before resection, isovolumetric thinning occurred in the aneurysm as well as bordering segments, with delta t ranging from -17 +/- 5% (+/- SEM) in the anteroseptal segment to 12 +/- 6% posterolaterally (p less than 0.05). The isovolumetric bulge was followed by late-systolic thickening, however, with delta t ranging from 13 +/- 7% to 27 +/- 8% (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Short‐Term Malnutrpition in Neonatal Rabbits. I. Brush Border Enzymes

SummarySeventy‐two hour starvation in neonatal rabbits was studied. Fasted animals received no feeds, only water every 8 h for 72 h. Fed animals were suekled by the dam. I here was no difference in birth weight, serum albumin, blood urea nitrogen, electrolytes, or urine specific gravity between led and fasted animals. Weight at 72 hr was less in lasted (p &lt; 0.01) than fed rabbits. Serum cortisol (p &lt; 0.05) and corticosterone (p &lt; 0.01) levels were higher in the fasted group. Proximal and distal small bowel homogenates had less DNA and protein (p &lt; 0.01) in the lasted group, but the protein DNA ratio was the same in the proximal and distal small bowel homogenates from both groups. Sucrase (E.C.3.2.1.26) specific activity was significantly increased in proximal small bowel homogenates from the fasted group (p &lt; 0.01) but was the same in distal small bowel homogenates from both groups. Sucrase total activity per proximal segment was the same in fed and fasted animals but was significantly less per segment in distal small bowel homogenates from fasted animals. Alkaline phosphatase (E.C.3.1.3) total and specific activity was decreased in proximal (p &lt; 0.01 ) and distal (p &lt; 0.05) small bowel homogenates from the lasted group. Lactase (E.C.3.2.1.23) total activity was decreased in proximal and distal (p &lt; 0.01) small bowel homogenates from the lasted group but lactase specific activity was unchanged. Thus, a brief period of malnutrition in neonatal animals can result in a variety of regional functional changes in the gastrointestinal mucosa.

Short-term malnutrition in neonatal rabbits. I. Brush border enzymes.

Seventy-two hour starvation in neonatal rabbits was studied. Fasted animals received no feeds, only water every 8 h for 72 h. Fed animals were suckled by the dam. There was no difference in birth weight, serum albumin, blood urea nitrogen, electrolytes, or urine specific gravity between fed and fasted animals. Weight at 72 hr was less in fasted (p less than 0.01) than fed rabbits. Serum cortisol (p less than 0.05) and corticosterone (p less than 0.01) levels were higher in the fasted group. Proximal and distal small bowel homogenates had less DNA and protein (p less than 0.01) in the fasted group, but the protein/DNA ratio was the same in the proximal and distal small bowel homogenates from both groups. Sucrase (E.C.3.2.1.26) specific activity was significantly increased in proximal small bowel homogenates from the fasted group (p less than 0.01) but was the same in distal small bowel homogenates from both groups. Sucrase total activity per proximal segment was the same in fed and fasted animals but was significantly less per segment in distal small bowel homogenates from fasted animals. Alkaline phosphatase (E.C.3.1.3) total and specific activity was decreased in proximal (p less than 0.01) and distal (p less than 0.05) small bowel homogenates from the fasted group. Lactase (E.C.3.2.1.23) total activity was decreased in proximal and distal (p less than 0.01) small bowel homogenates from the fasted group but lactase specific activity was unchanged. Thus, a brief period of malnutrition in neonatal animals can result in a variety of regional functional changes in the gastrointestinal mucosa.

Effects of the acylcarnitine-transferase blocking agent sodium 2[5-(4-chlorophenyl)-pentyl]-oxirane-2-carboxylate (POCA) on metabolism and regional function in the underperfused canine myocardium.

We investigated the effects of sodium 2[5-(4-chlorophenyl)-pentyl]-oxirane-2-carboxylate (POCA) on regional myocardial function and metabolism in anesthetized, thoracotomized dogs subjected to a 53.5% reduction in flow through the circumflex branch of the left coronary artery (LCX). Regional function in the area supplied by the LCX and the left anterior descending coronary artery (LAD) was assessed by means of two pairs of subendocardially inserted ultrasonic transducers. Hemoglobin content, oxygen saturation, pH, PCO2, PO2, lactate, glucose, and free fatty acids were determined in arterial and local venous blood obtained from the area supplied by the LCX. POCA (20 mg/kg/20 min i.v.) induced a transient decrease in left ventricular power and cardiac output. Arterial free fatty acid (FFA) levels increased continuously throughout the experiment, whilst arterial glucose levels showed a continuous decrease. FFA uptake, lactate release, and oxygen uptake were reduced in the underperfused area by POCA. At the same time, POCA induced a transient increase in end-diastolic segment length and a sustained decrease in systolic shortening during the ejection phase in the underperfused area. No changes in regional function were observed in the area perfused by the nonconstricted LAD.

Regional ischemic ventricular dysfunction in myocardium supplied by a narrowed coronary artery with increasing halothane concentration in the dog.

The effects of increasing inspired halothane concentration (0.5, 1.0, 1.5, 2.0 per cent) upon left ventricular myocardium supplied by a critically narrowed coronary artery and a normal coronary artery were studied in 11 open-chested dogs. Regional ventricular function was measured by continuous recording of ventricular segment length using pairs of implanted miniature ultrasonic length detectors in the left anterior descending coronary artery (LAD) and left circumflex coronary artery (LC) territories before and during critical stenosis of the LAD by a micrometer-controlled snare. Critical narrowing was documented by ischemic regional ventricular function (i.e., post-systolic shortening; systolic lengthening) limited to the LAD territory when FIO2 = 0 for 90 seconds. Hemodynamic variables (aortic, left atrial and left ventricular pressure, and heart rate) were measured, ECG lead II was recorded, and the first derivative of left ventricular pressure (LV dP/dt) and coronary perfusion pressure derived for each halothane concentration before and during LAD narrowing. Increasing halothane was associated with equivalent progressive depression of global ventricular function before and during LAD constriction. Prior to LAD constriction, no ischemic changes in regional function occurred. Regional ventricular function was normal during 0.5 percent halothane in the presence of LAD constriction. With increasing halothane during LAD constriction, ischemic regional ventricular function was observed in the LAD territory in eight of eleven hearts, whereas regional ventricular function remained normal in the LC territory. The epicardial ECG was recorded in three dogs and was insensitive as an indicator of ischemia, becoming abnormal only after severe ischemic changes were established. In these studies, in which heart rate remained constant, arterial blood pressure and LV dP/dt decreased, and left ventricular end-diastolic pressure increased, decrease in blood flow and oxygen delivery due to a lower perfusion pressure distal to the coronary artery narrowing appears to be primarily responsible for the observations. The authors hypothesize that clinically unapparent episodes of regional myocardial ischemia distal to narrowed coronary arteries may be an important cause of perioperative myocardial infarction.