Jesus A. Bianco

Effects of Intra-Aortic Balloon Counterpulsation on Cardiac Performance, Oxygen Consumption, and Coronary Blood Flow in Dogs

The effect of intra-aortic Counterpulsation (IACP) with a balloon upon myocardial oxygen consumption (MV·o2), coronary blood flow (TCF), and left ventricular performance was studied in 23 anesthetized canine right heart bypass preparations at constant heart rate and cardiac output. In nonhypotensive, nonTCF-limited preparations, IACP produced a fall in left ventricular peak systolic pressure (LVP) and a decrease in MV·o2 (-1.1 ± 0.2 (SE) ml/min/100 g LV). In these animals there was little steady state change in TCF (-5.6±5.9 ml/min), secondary to autoregulation by the coronary vascular bed. Left ventricular end-diastolic pressure (LVEDP) fell if elevated but exhibited little change if initially normal. However, in hypotensive preparations, in which left ventricular performance was substantially limited by a decreased TCF, IACP produced a striking increase in TCF (+40.9 ± 8.6 ml/min) accompanied by an increase in MV·o2 (+1.2±0.3 ml/min/100 g LV). Elevated LVEDPs fell substantially toward normal. Directiona...

Relative Contributions of the Atrial Systole-Ventricular Systole Interval and of Patterns of Ventricular Activation to Ventricular Function during Electrical Pacing of the Dog Heart

In areflexic canine right heart bypass preparations, little difference in ventricular function was observed as a result of atrial pacing, sequential atrioventricular pacing, or atrial-His bundle pacing at an appropriate atrial systole-ventricular systole (As-Vs) interval. Ventricular function was depressed during ventricular pacing and during atrioventricular pacing with an inappropriate As-Vs interval. In areflexic isovolumic left ventricle preparations, ventricular function was depressed during ventricular pacing compared to atrial pacing, and changes in the As-Vs interval during atrioventricular pacing were accompanied by changes in ventricular function only in association with changing patterns of ventricular activation. In animals with heart block under conditions of right heart bypass, wherein changes in the pattern of ventricular activation were precluded during atrioventricular pacing, ventricular function deteriorated pari passu with shortening of the As-Vs interval. These data indicate that both the temporal relation between atrial and ventricular contraction and the pattern of ventricular activation importantly influence ventricular function during cardiac pacing. The marked changes in ventricular function observed as a function of the As-Vs interval, for any given pattern of electrical activation, suggest that the As-Vs interval is the more important determinant of ventricular function during cardiac pacing.

Radioguided parathyroidectomy in patients with secondary and tertiary hyperparathyroidism.

BACKGROUND To date there have been no reports on the feasibility of radioguided parathyroidectomy (RGP) in patients with secondary and tertiary hyperparathyroidism. METHODS Twenty-three consecutive patients with secondary (n=5) or tertiary hyperparathyroidism (n=18) underwent RGP. Patients were injected with 10 mCi of technetium 99-sestamibi before surgery. All parathyroid glands were localized during operation with a neoprobe. RESULTS The mean patient age was 50+/-3 years. The mean preoperative calcium and intact parathyroid hormone levels were 11.0+/-0.3 mg/dL and 400+/-107 pg/mL, respectively. Eighteen patients had 3- or 4-gland hyperplasia, 2 had double adenomas, 2 had forearm graft hyperplasia, 1 had 6-gland disease, and 3 had ectopic glands. All hyperplastic glands had ex vivo counts >20% of background (mean, 63%+/-6%), making frozen section unnecessary. When compared with 66 historical control subjects who underwent surgery without radioguidance for tertiary hyperparathyroidism, patients undergoing RGP had decreased operative times (96+/-8 minutes vs 151+/-15 minutes; P<.001) and lengths of stay (1.3+/-0.1 days vs 3.7+/-0.3 days; P<.001). CONCLUSIONS RGP in patients with secondary and tertiary hyperparathyroidism is feasible, may reduce operative time, and permits omission of frozen section. Thus RGP appears to be a useful adjunct in the treatment of secondary and tertiary hyperparathyroidism.

Measurement of Coronary Blood Flow and Flow Reserve Using Magnetic Resonance Imaging

PURPOSE It was the purpose of this study to demonstrate the feasibility of performing coronary artery flow and coronary flow reserve (CFR) measurements in normal human volunteers using a magnetic resonance (MR) phase contrast technique. MATERIALS AND METHODS Coronary flow rate, flow velocity, peak flow and CFR were determined at rest and during pharmacologically induced hyperemia in 10 healthy volunteers. The flow measurements were obtained during a single breath-hold by using a fast, prospectively gated, segmented k-space gradient-echo phase contrast acquisition with view sharing (FASTCARD PC) that was modified to improve sampling of the diastolic flow. Data were processed using the standard phase difference (PD) processing techniques as well as a new complex difference (CD) flow measurement method intended to improve the accuracy of flow measurements in small vessels. RESULTS Mean hyperemic flow velocity (40 +/- 16 cm/s) and blood flow (3.9 +/- 1.5 ml/s) rates differed significantly from resting velocity (13 +/- 6.6 cm/s) and flow (1.1 +/- 0.4 ml/s) measurements (p < 0.0001). PD methods consistently measured larger flow rates at rest (24% larger, p < 0.0005) and stress (29% larger, p < 0.0001). CFR, calculated as the ratio of the mean PD flows (4.7 +/- 2.8), was higher than CFR calculated as the ratio of mean CD flows (4.2 +/- 1.8); however, the differences did not reach statistical significance (p = 0.07). Flow measurements performed in adjacent slices of the same vessel correlated well (r = 0.88). CONCLUSIONS Coronary flow and CFR measurements using the MR techniques are feasible and are similar to those reported in the literature for healthy volunteers.

Discordance between accumulation of C-14 deoxyglucose and T1–201 in reperfused myocardium

Radiolabeled deoxyglucose (FDG) has been advocated as a marker of viability of reperfused myocardium during acute infarction. However, data for such recommendation are few. We investigated cardiac deposition of C-14 deoxyglucose (C-14 DG) and of Thallium -201 (Tl-201) in rabbits subjected to coronary occlusion (15, 30, 60 or greater than 100 min) and reperfusion (75 min and 24 h). Measured myocardial concentrations of C-14 DG and Tl-201 in macroautoradiograms were quantitatively correlated in a 24 h reperfusion group with presence of myocardial necrosis evaluated by light microscopy. The major finding in this investigation was that with 30 min or 60 min of ischemia followed by reperfusion there were myocardial regions with significant hypoperfusion (Tl-201) and histologic necrosis. However, in the same myocardial areas, the deposition of C-14 DG was not correlated with the extent of necrosis (r = 0.27). Also, the deposition of C-14 DG in acute myocardial infarction was higher than that of Tl-201 (P = 0.05 by paired T test and by nonparametric Wilcoxons test). It was also demonstrated that when the occlusion time was varied (15-130 min) and early reperfusion was provided for 75 min or omitted altogether, the myocardial accumulation of Tl-201 was variable and that myocardial sequestration of C-14 DG was higher than perfusion in central and peripheral portions of the area-at-risk. These observations do not support a role for the use of radiolabeled deoxyglucose for the detection of myocardial viability in recently infarcted cardiac muscle.

Radioguided Parathyroidectomy for Recurrent Hyperparathyroidism Caused by Forearm Graft Hyperplasia

One of the surgical options for symptomatic secondary hyperparathyroidism is a total parathyroidectomy with forearm implantation. Recurrence can occur and is most likely caused by hyperplasia of the small fragments of parathyroid tissue implanted in the forearm muscle. Forearm graft hyperplasia can be detected using Tc‐99m sestamibi scanning of the forearm, which can show abnormal enhancement at the former graft site. In this report, we present the case of a 49‐year‐old gentleman with recurrent hyperparathyroidism caused by hyperplasia of forearm graft fragments. Unfortunately, no sutures or clips were placed at his initial surgery to identify the location of the parathyroid tissue in the forearm. Thus, we describe the first reported use of radioguided techniques using Tc‐99m sestamibi injection and intraoperative gamma probe to localize parathyroid fragments in the forearm muscle. During our initial exploration, we found that injection of the tracer in the operative arm leads to prohibitively high levels of background activity. During a second exploration, the tracer was injected in the lower extremity, minimizing the background in the forearm and allowing the gamma probe to clearly identify two areas of abnormal parathyroid tissue. The intraoperative radioprobe allowed quick identification and removal of the abnormal parathyroid tissue in a case that was made particularly challenging by the absence of marking sutures.

Can thallium-pertechnetate subtraction scanning play a role in the preoperative imaging for minimally invasive parathyroidectomy?

Purpose: Preoperative Tc-99m sestamibi scanning can identify candidates for minimally invasive parathyroid surgery. However, a significant number of patients with single gland disease have negative scans and are not considered for the minimally invasive procedure. Materials and Methods: To determine if T1-201/Tc-99m sodium pertechnetate subtraction scanning (TPSS) is a viable alternative imaging technique for patients with primary hyperparathyroidism (1° HPTH), we reviewed our experience. The outcomes of 100 consecutive patients with 1° HPTH who underwent preoperative TPSS and parathyroid exploration between 1995 and 2000 at our institution were retrospectively reviewed. Results: The mean preoperative calcium and parathyroid hormone levels were 10.8 mg/dL and 220 pg/mL, respectively. The overall cure rate was 96%. Single gland disease was present in 88%. Of the 100 patients studied, 15 underwent both a Tc-99m sestamibi scan and TPSS, whereas the other 85 had only the TPSS. Conclusions: The sensitivity and positive predictive value of the TPSS were 73.3% and 90.4%, respectively. In the patients undergoing both TPSS and Tc-99m sestamibi scans, the results concurred in 60%. However, in 20% of the remaining patients, TPSS correctly localized the abnormal parathyroid(s) when Tc-99m sestamibi failed. TPSS has a comparable sensitivity and positive predictive value to Tc-99m sestamibi scanning. In patients with a negative Tc-99m sestamibi scan, TPSS can provide additional localizing information. As a result of the high positive predictive value of TPSS, a single parathyroid gland localized by TPSS alone can then be approached by minimally invasive parathyroidectomy.

Effect of influenza immunization on CYP3A4 activity

A number of clinical reports of drug interactions with influenza vaccine have been made. We hypothesized that CYP3A4 activity would decrease following influenza immunization. Fifteen healthy subjects had erythromycin breath tests (ERMBT) and influenza antibody titer hemagglutinin inhibition assay (HIA) before and after receiving influenza vaccine. The mean age of the subjects was 31.9 years (S.D. 10.2). The change in ERMBT following influenza immunization was not significant (mean -4%, S.D. 17%, P=0.25). Influenza immunization does not significantly change CYP3A4 activity. Changes in serum drug concentrations noted previously after influenza immunization are either due to very small changes in CYP3A4 activity or other pharmacokinetic interactions.

Thallium-pertechnetate subtraction scanning in the preoperative localization of an ectopic undescended parathyroid gland.

Although bilateral exploration is highly effective in the treatment of primary hyperparathyroidism, minimally invasive parathyroidectomy has evolved into the procedure of choice when a single parathyroid lesion can be localized preoperatively. In this article, we discuss the utilization of thallium-pertechnetate subtraction scanning (TPSS) after technetium Tc-99m sestamibi scintigraphy failed to localize an ectopic parathyroid adenoma. Subsequently, radioguided resection of an undescended parathyroid adenoma inferior to the left submandibular gland was performed with surgical cure after a single procedure. This case report illustrates the importance of TPSS as a second-line modality in preoperative adenoma localization, thereby using minimally invasive techniques to successfully treat this patients primary hyperparathyroidism.

Physiologic and Clinical Significance of Myocardial Blood Flow Quantitation: What Is Expected from These Measurements in the Clinical Ward and in the Physiology Laboratory?

In this essay we review data on absolute quantitation of myocardial blood flow (MBF) in humans. Earlier work established that coronary heart disease (CAD) can be detected by coronary angiography and that this disease has characteristic features at rest and during stress, which indicate the linkage between regional metabolic needs and myocardial perfusion. In the 1970s myocardial perfusion was mapped in patients with radioxenon, but this method had significant technical limitations. About the same time, radioactive microspheres were introduced for cardiovascular research and investigations; these particles provided insights on MBF in acute infarction and ischemia, myocardial reperfusion, collateral circulation, myocardial blood flow during exercise, coronary flow reserve (CFR), and layer-to-layer distribution of MBF. Studies with microspheres also permitted investigators to establish the presence in the heart of MBF heterogeneity. Currently, there are several techniques that aim at extending these concepts into clinical investigation. Two of these techniques, i.e. Doppler coronary flow velocity and fast magnetic resonance imaging assess epicardial flow dynamics and CFR. Contrast myocardial echocardiography is another novel technique which has been useful in mapping the area at risk, reperfusion, myocardial viability and collateral circulation. This essay also considers the emerging technique of intracoronary ultrasound which has shown evidence of disease underestimation by conventional contrast angiography. Positron emission tomography (PET) is a noninvasive technique that uniquely and quantitatively maps myocardial perfusion and CFR. The latter can be computed before and after angioplasty. PET studies have further demonstrated that chronic myocardial ischemia does not exist as a distinct state in patients with CAD. From the above investigations the concept has arisen that not only is CAD an entity involving epicardial vessels but also, in a significant portion of patients, an abnormal microcirculation plays an important role in the pathogenesis of ischemic syndromes. PET studies have relatively low spatial resolution since they cannot resolve layer-to-layer absolute MBF.