Managing hypertension in urban underserved subjects using telemedicine--a clinical trial.

BACKGROUND: We evaluated an Internet- and telephone-based telemedicine system for reducing blood pressure (BP) in underserved subjects with hypertension. METHODS: A total of 241 patients with systolic BP ≥140 mm Hg were randomized to usual care (C; n = 121) or telemedicine (T; n = 120). The T group reported BP, heart rate, weight, steps/day, and tobacco use twice weekly. The primary outcome was BP control at 6 months. RESULTS: Average age was 59.6 years, average body mass index was 33.7 kg/m(2), 79% were female, 81% were African American, 15% were white, 53% were at or below the federal poverty level, 18% were smokers, and 32% had diabetes. Six-month follow-up was achieved in 206 subjects (C: 107, T: 99). Goal BP was achieved in 52.3% in C and 54.5% in T (P = .43). Systolic BP change (C: -13.9 mm Hg, T: -18.2; P = .118) was similar in both groups. Subjects in the T group reported BP 7.7 ± 6.9 d/mo. Results were not affected by age, sex, ethnicity, education, or income. In nondiabetic T subjects, goal BP was achieved in 58.2% compared with 45.2% of diabetic T subjects (P = .024). Nondiabetic T subjects demonstrated a greater reduction in systolic BP (T: -19 ± 20 mm Hg, C: -12 ± 19 mm Hg; P = .037). No difference in BP response between C and T was noted in patients with diabetes. CONCLUSION: In hypertensive subjects, engagement in a system of care with or without telemedicine resulted in significant BP reduction. Telemedicine for nondiabetic patients resulted in a greater reduction in systolic BP compared with usual care. Telemedicine may be a useful tool for managing hypertension particularly among nondiabetic subjects.

Reducing cardiovascular disease risk in medically underserved urban and rural communities.

OBJECTIVES: The aim of this study is to evaluate methods for lowering cardiovascular disease (CVD) risk in asymptomatic urban and rural underserved subjects. BACKGROUND: Medically underserved populations are at increased CVD risk, and systems to lower CVD risk are needed. Nurse management (NM) and telemedicine (T) systems may provide low-cost solutions for this care. METHODS: We randomized 465 subjects without overt CVD, with Framingham CVD risk >10% to NM with 4 visits over 1 year, or NM plus T to facilitate weight, blood pressure (BP), and physical activity reporting. The study goal was to reduce CVD risk by 5%. RESULTS: Three hundred eighty-eight subjects completed the study. Cardiovascular disease risk fell by ≥ 5% in 32% of the NM group and 26% of the T group (P, nonsignificant). In hyperlipidemic subjects, total cholesterol decreased (NM -21.9 ± 39.4, T -22.7 ± 41.3 mg/dL) significantly. In subjects with grade II hypertension (systolic BP ≥ 160 mm Hg, 24% of subjects), both NM and T groups had a similar BP response (average study BP: NM 147.4 ± 17.5, T 145.3. ± 18.4, P is nonsignificant), and for those with grade I hypertension (37% of subjects), T had a lower average study BP compared to NM (NM 140.4 ± 16.9, T 134.6 ± 15.0, P = .058). In subjects at high risk (Framingham score ≥ 20%), risk fell 6.0% ± 9.9%; in subjects at intermediate risk (Framingham score ≥ 10, < 20), risk fell 1.3% ± 4.5% (P < .001 compared to high-risk subjects). Medication adherence was similar in both high- and intermediate-risk subjects. CONCLUSIONS: In 2 underserved populations, CVD risk was reduced by a nurse intervention; T did not add to the risk improvement. Reductions in BP and blood lipids occurred in both high- and intermediate-risk subjects with greatest reductions noted in the high-risk subjects. Frequent communication using a nurse intervention contributes to improved CVD risk in asymptomatic, underserved subjects with increased CVD risk. Telemedicine did not change the effectiveness of the nurse intervention.

Treatment of patients with intermediate cardiovascular risk: Are clinical measures enough?

AIM: Clinical measures of cardiovascular disease risk (CVD) are important tools for establishing therapy to lower CVD risk. Risk assessment has come under criticism because clinical measures can underestimate or overestimate CVD risk. We assessed CVD risk in 252 subjects without evidence of CVD to establish therapy of one or more risk factors from clinical indications. The subjects all had intermediate CVD risk using the Framingham score. RESULTS: Average age was 59.1 years. 23.8% were smokers, 59.1% were hypertensive, 65.1% had hyperlipidemia. BMI was greater than 30 kg/M(2) in 56% and diabetes was present in 43.7%. In this cohort, 86.9% required therapy for hypertension or hyperlipidemia, and this proportion increased to 95.6% when subjects with diabetes were included. Of the remaining 4.4% (11 subjects), 7 reached intermediate risk based on cigarette smoking and 4 based on age >65 years old. Among diabetics, 94/110 had another risk factor and would require statin and ACE or ARB therapy. CONCLUSIONS: Of subjects at intermediate risk for CVD, 98.4% would not require further testing to decide on therapy to lower CVD risk. Although 16 diabetic subjects had no other risk factors, current guidelines suggest that these subjects should be treated to reduce CVD risk.

Managing heart failure care using an internet-based telemedicine system.

BACKGROUND: Managing patients with heart failure (HF) is labor intensive, and follow-up is often inadequate to detect day-to-day changes that ultimately lead to decompensation. We tested the effect of an Internet-based telemedicine (T) system that provides frequent surveillance and increased communicate between HF patients and their provider on frequency of hospitalization in a cohort of patients with advanced HF. METHODS AND RESULTS: HF patients in NYHA Class II-IV were randomized to usual care (UC, n = 24) or T (T plus UC, n = 24) and followed for 1 year. Office visits, emergency department visits, hospitalizations, telephone calls, and number of Internet communications were measured over the 1-year period. Left ventricular ejection fraction (EF) was assessed by echocardiography in both groups. For T, mean age was 53.2 +/- 2.0 years (72% male, 61% Caucasian, 39% African American). For UC, mean age was 54.1 +/- 2.6 years (76% male, 72% Caucasian, 14% African American, and 14% Hispanic). HF etiologies and EF were similar in both groups. During the 12-month period, UC had 74 total phone calls to the practice, whereas T had 88 telephone calls plus 1887 telemedicine data messages (6.5 messages/patient/month). ER visits were lower in the T group (T 5, UC 12; P < .05). Hospital admissions (T 24, C 40; P = .025) and total hospital days (T 84, UC 226 days; P < .005) were lower in T. Unscheduled clinic visits (T 13, UC 13; P = NS) and scheduled clinic visits (T 78, UC 94; P = NS) were similar in both groups. CONCLUSIONS: Frequent monitoring and patient management using a telemedicine system may help to reduce hospitalizations, hospital days, and emergency department visits.

Cardiovascular disease knowledge and risk perception among underserved individuals at increased risk of cardiovascular disease.

BACKGROUND: Cardiovascular disease (CVD) risk factor awareness and knowledge are believed to be prerequisites for adopting healthy lifestyle behaviors. The purpose of this study was to examine knowledge of CVD risk factors and risk perception among individuals with high CVD risk. METHODS: The sample consisted of inner city and rural medically underserved patients at high risk of CVD. To be eligible for the trial, subjects were required to have a 10% or greater CVD risk on the Framingham risk score. Knowledge of CVD was assessed with a 29-item questionnaire created for this study. Subjects also rated their perception of risk as compared with individuals of their own sex and age. RESULTS: Data were collected from 465 subjects (mean [SD] age, 60.5 [10.1] years; mean [SD] Framingham risk score, 17.3% [9.5%]). The mean (SD) CVD knowledge score was 63.7% (14.6%), and mean (SD) level of risk perception was 0.35 (1.4). Men and women had similar Framingham risk scores, but women perceived their risk to be significantly higher than that of their male counterparts. Women were also more knowledgeable than men about CVD. Urban participants had significantly higher actual risks than did their rural counterparts (18.2% [10.7%] vs 16.0% [8.9%], respectively; P = .01) but were significantly less knowledgeable about heart disease and also perceived their risk to be lower. CONCLUSIONS: These results indicate a low perception of risk and cardiovascular knowledge especially among men and inner city residents. Innovative educational strategies are needed to increase risk factor knowledge and awareness among at-risk individuals.

Accuracy of blood pressure measurements transmitted through a telemedicine system in underserved populations.

In underserved populations, inadequate surveillance and treatment allows hypertension to persist until actual cardiovascular events occur. Thus, we developed an Internet-based telemedicine system to address the suboptimal control of hypertension and other modifiable risk factors. To minimize cost, the subjects used home monitors for blood pressure (BP) measurements and entered these values into the telemedicine system. We hypothesized that patients could accurately measure their BP and transmit these values via a telemedicine system. Inner city and rural subjects (N = 464; 42% African-American or Hispanic) with 10% or greater 10-year risk of cardiovascular disease and with treatable risk factors were randomized into two groups, control group (CG) and telemedicine group (TG). Each subject received a home sphygmomanometer with memory. The TG recorded and entered BP at least weekly. During office visits, the BP meters were downloaded and recorded BP compared to BP values transmitted via telemedicine. The telemedicine (T) BP values were similar to the meter recorded (R) values (T: systolic/diastolic BP 133.4 +/- 11.1/77.5 +/- 6.8 mm Hg, and R: systolic/diastolic BP 136.4 +/- 11.9.4/79.7 +/- 7.5 mm Hg). The percent error was <1% for both systolic (-0.02 +/- 0.04%) and diastolic (-0.03 +/- 0.04%) BP. Lastly, the telemedicine BP values were similar to the office (O) BP values for systolic and diastolic BP (T: systolic/diastolic BP 133.4 +/- 11.1/77.5 +/- 6.8 mm Hg, and O: systolic/diastolic BP 136.3 +/- 20.5/78.1 +/- 10.5 mm Hg). In underserved populations, this inexpensive approach of patients using a home monitor and entering these values into a telemedicine system provided accurate BP data.

Use of an internet-based telemedicine system to manage underserved women with gestational diabetes mellitus.

BACKGROUND: Internet technology has been proven to be a successful tool for the management of patients with multiple medical conditions. The purpose of this study was to demonstrate the feasibility of monitoring glucose control in indigent women with gestational diabetes mellitus (GDM) over the Internet. METHODS: Women with GDM were randomized to either the Internet group (n = 32) or the control group (n = 25). Patients in the Internet group were provided with computers and/or Internet access if needed. A website was established for documentation of glucose values and communication between the patient and the health care team. Women in the control group maintained paper logbooks, which were reviewed at each prenatal visit. Maternal feelings of diabetes self-efficacy were assessed at study entry and again before delivery. RESULTS: Women in the Internet group accessed the system and sent on average 21.8 (+/- 16.9) sets of data. There was no difference between the two groups in regards either fasting or post-prandial blood glucose values, although more women in the Internet group received insulin therapy (31% vs. 4%; P <0.05). There were also no significant differences in pregnancy and neonatal outcomes between the two groups. Women in the Internet group demonstrated significantly higher feelings of self-efficacy at the study's end. CONCLUSIONS: The benefit of monitoring blood glucose in indigent women with GDM via the Internet was limited by their infrequent use of the telemedicine system. Although system use was not associated with improved pregnancy outcomes, women in the telemedicine group did experience enhanced feelings of diabetes psychosocial self-efficacy.

Left ventricular reshaping: effects on the pressure-volume relationship.

OBJECTIVE: We tested whether the CardioClasp device (CardioClasp, Inc, Cincinnati, Ohio), a non-blood contact device, would improve left ventricular contractility by acutely reshaping the left ventricle and reducing left ventricular wall stress. METHODS: In dogs (n = 6) 4 weeks of ventricular pacing (210-240 ppm) induced severe heart failure. Left ventricular function was evaluated before and after placement of the CardioClasp device, which uses 2 indenting bars to reshape the left ventricle. Hemodynamics, echocardiography, and Sonometrics crystals dimension (Sonometrics Corporation, London, Ontario, Canada) were measured at steady state and during inferior vena caval occlusion. RESULTS: The CardioClasp device decreased the left ventricular end-diastolic anterior-posterior dimension by 22.8% +/- 1.9%, decreased left ventricular wall stress from 97.3 +/- 22.8 to 67.2 +/- 7.7 g/cm(2) (P =.003), and increased the fractional area of contraction from 21.3% +/- 10.5% to 31.3% +/- 18.1% (P =.002). The clasp did not alter left ventricular end-diastolic pressure, left ventricular pressure, left ventricular dP/dt, or cardiac output. With the CardioClasp device, the slope of the end-systolic pressure-volume relationship was increased from 1.87 +/- 0.47 to 3.22 +/- 1.55 mm Hg/mL (P =.02), the slope of preload recruitable stroke work versus end-diastolic volume was increased from 28.4 +/- 11.0 to 44.1 +/- 23.5 mm Hg (P =.02), and the slope of maximum dP/dt versus end-diastolic volume was increased from 10.6 +/- 4.6 to 18.6 +/- 7.4 mm Hg x s(-1) x mL(-1) (P =.01). The CardioClasp device increased the slope of the end-systolic pressure-volume relationship by 68.0% +/- 21.7%, the slope of preload recruitable stroke work versus end-diastolic volume by 50.7% +/- 18.1%, and the slope of maximum dP/dt versus end-diastolic volume by 85.7% +/- 28.9%. CONCLUSIONS: The CardioClasp device decreased left ventricular wall stress and increased the fractional area of contraction by reshaping the left ventricle. The CardioClasp device was able to maintain cardiac output and arterial pressure. The clasp increased global left ventricular contractility by increasing the slope of the end-systolic pressure-volume relationship, the slope of preload recruitable stroke work versus end-diastolic volume, and the slope of maximum dP/dt versus end-diastolic volume. In patients with heart failure, the CardioClasp device might be effective for clinical application.

Left ventricular systolic performance in failing heart improved acutely by left ventricular reshaping.

OBJECTIVE: If the geometric distortion during dilated heart failure could be corrected, the tension on the myocytes would be decreased, thereby leading to an improvement in left ventricular systolic function. We tested the effects of the CardioClasp (CardioClasp Inc, Pine Brook, NJ), a left ventricular reshaping device, on the failing heart, and our empirical data were compared with computationally derived data. METHODS: Heart failure was induced by 4-week rapid cardiac pacing. At the terminal experiment, an isolated failing heart preparation (isovolumic contraction, n = 5) or an intact failing heart in vivo (n = 7) was used. The effects of the reshaping device on left ventricular performance were assessed by the slopes (Ees) of the left ventricular end-systolic pressure-volume relations, hemodynamics, and echocardiograph before and after placing the CardioClasp on the heart. The change in Ees as the result of left ventricular reshaping was also estimated from computed theoretical analysis and compared with empirical data. RESULTS: There was a significant change in left ventricular dimension after placing the CardioClasp on the heart. In isolated heart preparation, Ees significantly increased from 1.40 +/- 0.44 mm Hg/mL to 2.42 +/- 0.63 mm Hg/mL after placing the device on the heart but returned to the baseline level (1.46 +/- 0.27 mm Hg) after removing it. Left ventricular developed pressure and left ventricular fractional area shortening were significantly increased as the result of left ventricular reshaping. Ees derived from computed theoretical analysis was highly correlated with confirming empirical data. CONCLUSIONS: The CardioClasp can reshape the left ventricle and improve left ventricular systolic performance in failing hearts.

Early and late results of left ventricular reshaping by passive cardiac-support device in canine heart failure.

BACKGROUND: We tested whether the CardioClasp, a passive non-blood-contacting device could decrease excessive geometric burden in dilated cardiomyopathy and improve left ventricular systolic function and contractility by reshaping the left ventricle (LV) and by decreasing LV wall stress (LVWS) without decreasing arterial blood pressure. METHODS: In mongrel dogs (n = 6, the early group; n = 6, the chronic group; 25-27 kg), 4 weeks of rapid right ventricular pacing (210 to 240 bpm) induced dilated cardiomyopathy with heart failure. In the early group, we used hemodynamic data and echocardiography to evaluate LV systolic function immediately after placing the CardioClasp device. In the chronic group, we also evaluated LV systolic function immediately after placing the device on dilated hearts and then left the device in place for 30 days. At the end of 30 days, before explantation of the device, we again assessed LV systolic function. We measured fractional area of contraction (FAC), LVWS, and hemodynamic data in both groups. RESULTS: In the early group, use of the CardioClasp device decreased the LV end-diastolic anterior-to-posterior dimension by 27.8% +/- 2.6% at implantation (p < 0.05). In the chronic group, use of the CardioClasp decreased the LV end-diastolic anterior-to-posterior dimension by 19.4% +/- 2.0% at implantation (p < 0.05) and by 22.0% +/- 3.10% at explantation (p < 0.05). Use of the CardioClasp did not alter LV end-diastolic and peak pressure, LV dP/dts, or cardiac output at implantation or at explantation. In the early group, use of the CardioClasp decreased the LVWS by 43.4% +/- 3.1% at implantation (p < 0.05). In the chronic group, LVWS decreased by 28.8% +/- 2.1% at implantation (p < 0.05) and by 43.3% +/- 5.2% at explantation (p < 0.05). In the early group, FAC increased significantly, by 28.9% +/- 7.8% at implantation (p < 0.05). In the chronic group, FAC increased significantly, by 18% +/- 12% at implantation (p < 0.05) and by 19% +/- 12% at explantation (p < 0.05). CONCLUSIONS: As expected, use of the CardioClasp device increased FAC and decreased LVWS by reshaping the LV. Use of the CardioClasp device maintained cardiac output and arterial pressure. In 30-day experiments, the increased FAC and decreased LVWS were maintained at explantation.

CardioClasp: a new passive device to reshape cardiac enlargement.

In dilated heart failure, geometric distortions place an extra load on the myocardial cells. If this extra burden can be eliminated, the myocardial wall stress would decrease leading to improved systolic ventricular performance. In a dilated heart failure model, we wanted to see whether the CardioClasp (which uses two indenting bars to reshape the left ventricle [LV] as two widely communicating "lobes" of reduced radius) could improve systolic performance by passively reshaping the LV and reducing the wall stress. In mongrel dogs (n = 7; 25-27 kg), rapid ventricular pacing (210 ppm 1st week to 240 ppm 4th week) induced dilated heart failure. After 4 weeks, LV performance was evaluated at baseline and with the CardioClasp by measuring LV end-diastolic and peak LV systolic pressure, LV +dP/dt, LV -dP/ dt, and cardiac output. With the Clasp on, LV wall stress was reduced to 58.6+/-3.5 from 108.3+/-8.2 g/cm2. The fractional area of contraction (FAC) with the Clasp on (28.4+/-4.4) was significantly increased (p < 0.05) from baseline (20.8+/-4.6) and consistent with improved systolic performance. Cardiac output, LV peak systolic and end-diastolic pressures, and regional myocardial blood flow were unaltered. The Clasp was able to acutely reshape the left ventricle, while preserving the contractile mass, and reduced the tension on the myocardial cells and increased the fractional area of contraction without decreasing the systolic blood pressure.

Factors affecting frequency of patient use of Internet-based telemedicine to manage cardiovascular disease risk.

We examined the frequency of use by patients of a web-based reporting system to monitor and control cardiovascular disease (CVD) risk factors. A total of 192 patients with intermediate or high CVD risk were categorized into four quartiles based on their frequency of use of the telemedicine reporting system over one year. The lowest frequency users (Quartile I) averaged 17 reporting days in one year and the highest frequency users (Quartile IV) averaged 211 reporting days in one year. Factors associated with more frequent use were overall knowledge of CVD (P = 0.014), blood lipids (P = 0.017), smoking (P = 0.036), higher scores in medication self-efficacy (P = 0.016) and higher income (P = 0.002). All quartiles showed trends of decreasing systolic blood pressure from hypertensive (≥140 mm Hg) to pre-hypertensive (<140) ranges. Patients were able to lower CVD risk with as few as two transmissions per month using the telemedicine system. Telemedicine reporting coupled with self-assessment of health status can promote a strong patient-provider partnership for managing the chronic risk factors of CVD.

Impact of a telemedicine system with automated reminders on outcomes in women with gestational diabetes mellitus.

BACKGROUND: Health information technology has been proven to be a successful tool for the management of patients with multiple medical conditions. The purpose of this study was to examine the impact of an enhanced telemedicine system on glucose control and pregnancy outcomes in women with gestational diabetes mellitus (GDM). SUBJECTS AND METHODS: We used an Internet-based telemedicine system to also allow interactive voice response phone communication between patients and providers and to provide automated reminders to transmit data. Women with GDM were randomized to either the telemedicine group (n=40) or the control group (n=40) and asked to monitor their blood glucose levels four times a day. Women in the intervention group transmitted those values via the telemedicine system, whereas women in the control group maintained paper logbooks, which were reviewed at prenatal visits. Primary outcomes were infant birth weight and maternal glucose control. Data collection included blood glucose records, transmission rates for the intervention group, and chart review. RESULTS: There were no significant differences between the two groups (telemedicine vs. controls) in regard to maternal blood glucose values or infant birth weight. However, adding telephone access and reminders increased transmission rates of data in the intervention group compared with the intervention group in our previous study (35.6±32.3 sets of data vs.17.4±16.9 sets of data; P<0.01). CONCLUSIONS: Our enhanced telemedicine monitoring system increased system utilization and contact between women with GDM and their healthcare providers but did not impact upon pregnancy outcomes.

Rural and urban characteristics impact cardiovascular risk reduction.

PURPOSE: Our aim was to provide a descriptive analysis of specific differences between rural and urban residents and the interaction between these differences and those who reduced cardiovascular disease (CVD) risk in response to intervention versus those who did not. METHODS: This study is a descriptive analysis comparing rural groups with urban groups and those who decreased CVD risk with those who did not. Two hundred five rural (median age = 64.0 years [interquartile = 57.0, 71.0], 56% men) and 183 urban (median age = 58.0 years [interquartile = 50.0, 65.0], 53% men) residents were included. RESULTS: Rural and urban groups differed (P < .05) for demographic, anthropometric, physiological, and health-related variables. Those who decreased CVD risk, regardless of rural or urban, had greater blood pressure, greater low-density lipoprotein cholesterol, lower walking distance, greater CVD risk score, greater metabolic syndrome score, and greater internal health locus of control (all P < .05). Interestingly, there were differences between those who decreased risk and those who did not within the rural and urban groups. Triglycerides, C-reactive protein, diabetes knowledge, risk perception, and outcome expectations were greater for the rural group who decreased their CVD risk versus those who did not (all P < .05). For the urban group, there was a greater powerful others locus of control for those who decreased CVD risk (P < .05). CONCLUSIONS: To maximize the likelihood of success, risk reduction intervention and educational strategies for urban and rural groups must be tailored to address unique demographic, physiological, and health-related characteristics.

Gender differences in cardiovascular risk factors and risk perception among individuals with diabetes.

PURPOSE: The purpose of this study was to examine gender-based differences in cardiovascular risk factors and risk perception among individuals with diabetes. METHODS: The sample consisted of patients with an established history of diabetes who were enrolled in a telemedicine trial to reduce cardiovascular disease (CVD) risk. All subjects had a 10% or greater risk on the Framingham risk index. Assessments included blood pressure, A1C, lipid profile, medication history, and knowledge and risk perception surveys. RESULTS: Data were available for 211 individuals with type 2 diabetes (88 men and 123 women). The women and men did not differ in age, body mass index, or Framingham risk. Only 37.4% of women and 40.9% of men were at an A1C target of <7%. Total cholesterol levels were significantly higher among women, and fewer women were at low-density lipoprotein or blood pressure targets. Knowledge of CVD was similar between the 2 sexes. However, women perceived their risk for CVD to be significantly higher than did men. CONCLUSION: Less favorable cardiovascular risk profiles are observed among women with diabetes as compared with their male counterparts. Multifaceted approaches to both diabetes management and education are needed to target CVD risk reduction among individuals with diabetes.

Cardiovascular simulation toolbox.

A toolbox for Matlab Simulink (trademark of Mathworks corp. etc.) was developed to simulate various models of flow in the cardiovascular system and study effects of different pathological conditions. The toolbox was based on well-known analog lumped models of blood flow in vessels, the varying elastance heart model, blood flow through vessels, shunts, and valves as well as models of oxygen exchange at lungs and tissue. The toolbox is modular providing the basic building blocks of the cardiovascular system. Parameters for the individual components may be set by the user to adapt the component to the simulated system. Several examples are shown. This modeling system is described and is also available for downloading as an open source for free use. The authors see this as the basis for wide collaboration and standardization in modeling. A web site will be available for accepting contributions from other researchers and to create a free exchange.

Right atrial effects on right ventricular ejection fraction derived from thermodilution measurements.

OBJECTIVE: The thermodilution technique provides a convenient means to monitor cardiac output, right ventricular (RV) ejection fraction (EF), and volumes at the bedside. To calculate RVEF from the pulmonary artery temperature curve, the bolus thermodilution technique assumes that right atrial (RA) temperature returns to baseline value within 1 beat following the cold saline injection. The authors hypothesized that this assumption is the reason why the thermodilution technique consistently underestimates RVEF. DESIGN: A theoretical analysis and animal study. SETTING: Laboratory, university, multi-institutional. PARTICIPANTS: Animals. INTERVENTIONS: Cold saline injections. MEASUREMENTS AND MAIN RESULTS: In 2 porcine experiments, after a rapid injection of cold saline into right atrium, RA temperature took several heartbeats to return to baseline. In a theoretical analysis, if after the cold saline injection RA temperature returned to baseline in 1 beat (RAEF = 1), then thermodilution-derived RVEF(T) = actual RVEF(A). In contrast, if RA temperature took several beats to return to baseline (RAEF = RVEF), then RVEF(T) consistently underestimated RVEF(A). A least square fit of RVEF(A) versus RVEF(T) resulted in RVEF(A) = 1.0 x RVEF(T) + 0.11. Applying this correction (adding 0.11 to RVEF(T)) to the data gave relatively small errors in estimating RVEF over a wide EF range. CONCLUSIONS: After injecting cold saline into the right atrium, RA temperature takes several heart beats to return to baseline temperature, leading to underestimating RVEF and overestimating RV volumes. The pulsed thermal energy approach by injecting heat into the RV avoids these problems, but the impact of its small temperature signal on RVEF measurements needs to be determined.