**5. Second heart failure in women**

0 10 20 30 40

**Standing from Supine**

**Return to Supine**

**Time (minutes)**

**Figure 2.** Fractional blood volume changes associated with postural shifts in young adult men. *After Hagan, et al.,*

The net effect of these various processes is that 500-600 ml of blood pools into the lower limb veins within 2-3 minutes after attaining upright posture, while increased filtration from the capillaries reduces blood fluid volume by an additional 750 ml over the following 30-40 minutes, resulting in well over 1L decrease in effective circulatory system volume. The upright human therefore is confronted with three significant challenges with respect to maintaining adequate CO. First, fluid pooling into the lower limb veins and dependent tissues rapidly reduces effective blood fluid volume. Second, the fluid pressure available to return blood to the heart from the lower extremities remains at little more than 20 mmHg, which is incapable of overcoming the 80 mmHg of hydrostatic pressure created by the venous fluid column. Third, the high compliance of human skin allows these conditions to become exacerbated over the course of the day through interstitial fluid build up. This stress of upright posture is particu‐ larly challenging for women in that they have both more compliant veins [9], and somewhat

The cardiovascular challenges of upright posture are, in part, overcome by neuro-humorally mediated venoconstriction which limits venous pooling, though vasoconstriction has essen‐

0.84

*(1978) J. Appl. Physiol. 45:414-417*

more compliant skin [10].

**4. Soleus muscle anatomy/physiology**

0.86

0.88

0.90

0.92

**Serum Volume**

0.94

0.96

0.98

1.00

1.02

268 Cardiomyopathies

The essential role of non-locomotory based calf muscle pumping (i.e. second heart activity) in maintaining CO when individuals are in quiet upright posture, raises the question of the extent to which second heart activity varies within the population. Recent studies in our laboratory have focused on identifying the extent of second heart insufficiency in adults, with a particular focus on the prevalence of second heart failure in women. The predictive ability of resting heart rate in identifying women at greatest risk of experiencing coronary events suggests that tracking heart rate during the transition from standing to quiet sitting should be an effective means to quantify second heart capability. Moving from a standing to seated position repre‐ sents a decrease in both physical stress on the cardiovascular system (i.e. a reduction in the hydrostatic forces operating on the venous fluid column and therefore a reduction in pooling forces), and a reduction in physiologic stress (i.e. reduced metabolic activity). Quiet sitting, therefore, should result in a decrease in heart rate in otherwise healthy individuals.

We monitored heart rate in adult women (N=20) for 20 minutes following a transition from standing to quiet sitting [15]. Initial heart rate in this population of self-reported healthy women (average age = 52±4 years) was 77.5±3.5 bpm. In nine of these women (45%), heart rate decreased 1-8 bpm as expected (Figure 3) [15]. However, in 55% of the tested women (N=11), 20 minutes of quiet sitting led to a 6-12 bpm increase in heart rate (avg. 8.3 ± 0.5 bpm). Consistent with this increase in resting heart rate, brachial systolic blood pressure in this group of women was observed to fall by average 9.5 ± 1.8mmHg from an initial average pressure of 122.4 mmHg (±3.6 mmHg). Revision: FINAL **Figure 3.** Change in systolic blood pressure in healthy adult women following 20 minutes of quiet sitting. *From Madhavan, et al., 2005.* 

**Figure 3.** Change in systolic blood pressure in healthy adult women following 20 minutes of quiet sitting. From Mad‐ *havan, et al., 2005.*

Though approximately 50 percent of women appear to be able to maintain adequate fluid return from the lower limbs to support CO during 20 minutes of quiet sitting, 20 minutes is a

20

relatively short time period in the context of typical durations of sitting which most individuals experience during the day, and so does not directly address the challenge women face during extended upright posture given the high venous and skin compliances previously discussed. To address the impact of extended orthostatic stress, we have monitored beat-to-beat blood pressure changes during quiet sitting periods of over 30 minutes [16]. This research was motivated by recent reports of delayed orthostatic hypotension (DOH), a condition observed in 40% of individuals with symptoms of orthostatic intolerance, but with no evidence of acute orthostatic hypotension as assessed through traditional tilt-table testing [17]. We have observed that among women who appear to be able to maintain CO during quiet sitting, for approximately 30% of such women this capability is transient. We observe in these women that following 20-30 minutes of sustained quiet sitting, fluid return to the heart rapidly falls and resting blood pressure cannot be maintained (Figure 4) [16]. This inability to maintain resting blood pressure is particularly striking with respect to diastolic pressure as the average diastolic pressure in this group was found to fall to an average of 53 mmHg (±0.9mmHg) after 30 minutes of quiet sitting (Figure 5) [16], a value well below that necessary to adequately

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**Figure 4.** Typical blood pressure response to 30 minutes of quiet sitting in an adult woman with delayed orthostatic

regulate cerebral perfusion.

hypotension. *From Madhavan et al., 2008*.

relatively short time period in the context of typical durations of sitting which most individuals experience during the day, and so does not directly address the challenge women face during extended upright posture given the high venous and skin compliances previously discussed. To address the impact of extended orthostatic stress, we have monitored beat-to-beat blood pressure changes during quiet sitting periods of over 30 minutes [16]. This research was motivated by recent reports of delayed orthostatic hypotension (DOH), a condition observed in 40% of individuals with symptoms of orthostatic intolerance, but with no evidence of acute orthostatic hypotension as assessed through traditional tilt-table testing [17]. We have observed that among women who appear to be able to maintain CO during quiet sitting, for approximately 30% of such women this capability is transient. We observe in these women that following 20-30 minutes of sustained quiet sitting, fluid return to the heart rapidly falls and resting blood pressure cannot be maintained (Figure 4) [16]. This inability to maintain resting blood pressure is particularly striking with respect to diastolic pressure as the average diastolic pressure in this group was found to fall to an average of 53 mmHg (±0.9mmHg) after 30 minutes of quiet sitting (Figure 5) [16], a value well below that necessary to adequately regulate cerebral perfusion.

tracking heart rate during the transition from standing to quiet sitting should be an effective means to quantify second heart capability. Moving from a standing to seated position repre‐ sents a decrease in both physical stress on the cardiovascular system (i.e. a reduction in the hydrostatic forces operating on the venous fluid column and therefore a reduction in pooling forces), and a reduction in physiologic stress (i.e. reduced metabolic activity). Quiet sitting,

We monitored heart rate in adult women (N=20) for 20 minutes following a transition from standing to quiet sitting [15]. Initial heart rate in this population of self-reported healthy women (average age = 52±4 years) was 77.5±3.5 bpm. In nine of these women (45%), heart rate decreased 1-8 bpm as expected (Figure 3) [15]. However, in 55% of the tested women (N=11), 20 minutes of quiet sitting led to a 6-12 bpm increase in heart rate (avg. 8.3 ± 0.5 bpm). Consistent with this increase in resting heart rate, brachial systolic blood pressure in this group of women was observed to fall by average 9.5 ± 1.8mmHg from an initial average pressure of

**Figure 3.** Change in systolic blood pressure in healthy adult women following 20 minutes of

**Figure 3.** Change in systolic blood pressure in healthy adult women following 20 minutes of quiet sitting. From Mad‐

Though approximately 50 percent of women appear to be able to maintain adequate fluid return from the lower limbs to support CO during 20 minutes of quiet sitting, 20 minutes is a

20

therefore, should result in a decrease in heart rate in otherwise healthy individuals.

122.4 mmHg (±3.6 mmHg).

*havan, et al., 2005.*

quiet sitting. *From Madhavan, et al., 2005.* 

Revision: FINAL

270 Cardiomyopathies

**Figure 4.** Typical blood pressure response to 30 minutes of quiet sitting in an adult woman with delayed orthostatic hypotension. *From Madhavan et al., 2008*.

volume was continuously monitored for another 30 minutes. Two distinct subpopulations could be readily delineated according to their interstitial pooling behavior (Figure 6) [18]. Approximately half of the women experienced a significant decrease in calf fluid volume during the 30 minutes of quiet sitting at a median rate of 8 ml/hour, while half demonstrated

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23

significant calf swelling at a median rate of 12 ml/hour under these conditions.

into the calf at an average rate of 12ml/Hr. *From Goddard et al., 2008.* 

**Figure 6.** Interstitial fluid swelling of the calf during quiet sitting in a population (N=54) of

subjects experienced decreased calf fluid volume while 45% were found to pool interstitial fluid


**Figure 6.** Interstitial fluid swelling of the calf during quiet sitting in a population (N=54) of healthy adult women. Bi‐ modal distribution of pooling responses indicates that 55% of the subjects experienced decreased calf fluid volume while 45% were found to pool interstitial fluid into the calf at an average rate of 12ml/Hr. *From Goddard et al., 2008.*

While women who experience increased venous and interstitial pooling tend to be somewhat heavier, on average, than those that maintained their HR, BP, and calf volume during extended sitting, no significant differences in age, weight, or BMI have been identified. Moreover, these individuals do not demonstrate any frank failure of the circulatory system as measured by microvascular filtration rate, venous ejection fraction, venous filling index, or calf venous volume. Importantly, these responses do not reflect the behavior of just a small subset of women, but rather 50% or more of an otherwise healthy population of women. The most likely explanation for these observations appears to be inadequate calf muscle pump (second heart) activity, though this can only be confirmed through direct intervention by second heart

Rate of Change of Calf Fluid Volume (ml/hour)

healthy adult women. Bimodal distribution of pooling responses indicates that 55% of the

Revision: FINAL

0

stimulation.

1

2

3

4

Frequency Count (N=54)

5

6

N = 54

7

**Figure 5.** Time dependent changes in resting diastolic blood pressure in 29 adult women capable of maintaining HR and BP for the first 20 minutes of quiet sitting. Twenty women (70%) demonstrated a normotensive response to 30 minutes of the orthostatic stress of quiet sitting, while 9 (30%) demonstrated a distinct delayed orthostatic hypoten‐ sive response. *From Madhavan, et al., 2008*.

Similarly, a large fraction of women have been observed to experience extensive interstitial fluid pooling during quiet sitting. The high compliance of human skin, and women's skin in particular, creates a scenario in which extended duration orthostatic stress can permit exten‐ sive extravasation from the blood supply without the development of high tissue pressures which would inhibit this flow. To determine the extent to which this phenomenon could play a significant role in reducing fluid return to the heart, and correspondingly, maintaining CO, we utilized air plethysmography to follow calf volume over time in healthy adult women sitting quietly [18]. Fifty-four adult women (average age 46.7 ± 1.5 years) were recruited. After being placed in the supine position, the right calf was instrumented for air-pleythsmographic recording and the recording system was allowed to equilibrate to body temperature (approx‐ imately 30 minutes). The subject was then transitioned to the upright seated position and calf volume was continuously monitored for another 30 minutes. Two distinct subpopulations could be readily delineated according to their interstitial pooling behavior (Figure 6) [18]. Approximately half of the women experienced a significant decrease in calf fluid volume during the 30 minutes of quiet sitting at a median rate of 8 ml/hour, while half demonstrated significant calf swelling at a median rate of 12 ml/hour under these conditions. Revision: FINAL **Figure 6.** Interstitial fluid swelling of the calf during quiet sitting in a population (N=54) of healthy adult women. Bimodal distribution of pooling responses indicates that 55% of the subjects experienced decreased calf fluid volume while 45% were found to pool interstitial fluid

into the calf at an average rate of 12ml/Hr. *From Goddard et al., 2008.* 

**Figure 6.** Interstitial fluid swelling of the calf during quiet sitting in a population (N=54) of healthy adult women. Bi‐ modal distribution of pooling responses indicates that 55% of the subjects experienced decreased calf fluid volume while 45% were found to pool interstitial fluid into the calf at an average rate of 12ml/Hr. *From Goddard et al., 2008.*

**Figure 5.** Time dependent changes in resting diastolic blood pressure in 29 adult women capable of maintaining HR and BP for the first 20 minutes of quiet sitting. Twenty women (70%) demonstrated a normotensive response to 30 minutes of the orthostatic stress of quiet sitting, while 9 (30%) demonstrated a distinct delayed orthostatic hypoten‐

Similarly, a large fraction of women have been observed to experience extensive interstitial fluid pooling during quiet sitting. The high compliance of human skin, and women's skin in particular, creates a scenario in which extended duration orthostatic stress can permit exten‐ sive extravasation from the blood supply without the development of high tissue pressures which would inhibit this flow. To determine the extent to which this phenomenon could play a significant role in reducing fluid return to the heart, and correspondingly, maintaining CO, we utilized air plethysmography to follow calf volume over time in healthy adult women sitting quietly [18]. Fifty-four adult women (average age 46.7 ± 1.5 years) were recruited. After being placed in the supine position, the right calf was instrumented for air-pleythsmographic recording and the recording system was allowed to equilibrate to body temperature (approx‐ imately 30 minutes). The subject was then transitioned to the upright seated position and calf

sive response. *From Madhavan, et al., 2008*.

272 Cardiomyopathies

23 While women who experience increased venous and interstitial pooling tend to be somewhat heavier, on average, than those that maintained their HR, BP, and calf volume during extended sitting, no significant differences in age, weight, or BMI have been identified. Moreover, these individuals do not demonstrate any frank failure of the circulatory system as measured by microvascular filtration rate, venous ejection fraction, venous filling index, or calf venous volume. Importantly, these responses do not reflect the behavior of just a small subset of women, but rather 50% or more of an otherwise healthy population of women. The most likely explanation for these observations appears to be inadequate calf muscle pump (second heart) activity, though this can only be confirmed through direct intervention by second heart stimulation.

### **6. Intervention for second heart failure**

The soleus muscle operates primarily as an involuntary postural muscle whose activity is mediated by two different reflex arcs. In addition to the stretch reflex associated with venous sinus filling and emptying, the soleus is the primary lower leg muscle supporting upright stance. As such, its activity is mediated by a postural reflex arc originating on the frontal plantar surface. That is, pressure on the frontal aspect of the plantar surface during standing results in contraction of the soleus which pulls the body in the posterior direction; this unloads the frontal plantar surface, resulting in the soleus relaxing, and the body stops its posterior motion and begins to sway forward. While the stretch reflex appears to fail in a large fraction of adult women, very few of these individuals have any difficulty standing upright, indicating that the postural reflex arc controlling soleus activity is intact. This observation sets the stage for a convenient method to exogenously activate the soleus muscle.

Revision: FINAL

women. *From Madhavan, et al., 2005.*

Revision: FINAL


women. *From Goddard, et al., 2008.*





Change in Calf Fluid Volume (ml)



0

**Figure 7.** Efficacy of soleus muscle activation, through its postural reflex arc, to prevent blood

**Figure 7.** Efficacy of soleus muscle activation, through its postural reflex arc, to prevent blood pressure drop in adult


**- 4.35ml/hr**

N = 20

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Plantar Stimulation

Time (minutes)

**Figure 8.** Efficacy of second heart stimulation, through the plantar reflex, to reverse interstitial fluid pooling in adult

**Figure 8.** Efficacy of second heart stimulation, through the plantar reflex, to reverse interstitial

fluid pooling in adult women. *From Goddard, et al., 2008.* 

**+12.1ml/hr**

Quiet Sitting

**POPULATION STATISTICS Age: 46.7 +/- 10.5 years Weight: 75.5 +/- 13.9 kg Height: 1.64 +/- 0.05 m BMI: 27.9 +/- 5.0 kg/m2**

pressure drop in adult women. *From Madhavan, et al., 2005.* 

24

25

We have pursued this hypothesis that the postural reflex arc regulating soleus activity is intact in women with inadequate fluid return from the lower limbs, and our experimental results support both the contention that this postural reflex is operational, and that exogenous activation of this soleus reflex arc is sufficient to significantly increase venous and lymphatic return from the lower limbs. Initial work focused on identifying the characteristics of the stimulus necessary to activate the soleus reflex and we observed that a micromechanical stimulation of plantar surface at 45 Hz, with a magnitude of 10 micrometers or greater was sufficient. This observation is consistent with the activated mechanoreceptors on the foot being the Meisner corpuscles [19]. A stimulus of this nature applied to the frontal plantar surface was found to completely block the drop in BP and increase in HR observed in women who could not maintain fluid return from the lower limbs during quiet sitting (Figure 7) [15]. Further studies on the mechanism underlying these clinical observations have shown that the plantar reflex stimulation has no effect on lymphatic microfiltration rate, but rather increases the isovolumetric lymphatic pressure, as well as significantly enhancing perfusion in the lower leg, pelvic, and thoracic segments of the body [20].

As importantly, activation of the second heart (soleus) has been found to effectively in‐ hibit interstitial fluid pooling in adult women [17]. Following a 30 minute quiet sitting period during which a population of women (N=24) were observed to pool extensively (using air plethysmography), the subjects were exposed to 20 minutes of continuous plantar stimulation sufficient to activate the soleus muscle. Activation of the stimulus was found to result in an immediate drop in calf volume, which is interpreted to be due to the rapid decrease in venous volume (Figure 8) [17]. This rapid volume decrease was then followed by a sustained slower decrease in calf volume consistent with interstitial fluid migration to the initial lymphatics with subsequent ejection to the collecting lym‐ phatics and back to the heart. Sustained stimulation with continuous blood pressure monitoring confirms that the ejected fluid is returning to the heart per the associated in‐ crease in systolic blood pressure (Figure 9) [21].

24

25

**Figure 7.** Efficacy of soleus muscle activation, through its postural reflex arc, to prevent blood

Revision: FINAL

**6. Intervention for second heart failure**

274 Cardiomyopathies

convenient method to exogenously activate the soleus muscle.

leg, pelvic, and thoracic segments of the body [20].

crease in systolic blood pressure (Figure 9) [21].

The soleus muscle operates primarily as an involuntary postural muscle whose activity is mediated by two different reflex arcs. In addition to the stretch reflex associated with venous sinus filling and emptying, the soleus is the primary lower leg muscle supporting upright stance. As such, its activity is mediated by a postural reflex arc originating on the frontal plantar surface. That is, pressure on the frontal aspect of the plantar surface during standing results in contraction of the soleus which pulls the body in the posterior direction; this unloads the frontal plantar surface, resulting in the soleus relaxing, and the body stops its posterior motion and begins to sway forward. While the stretch reflex appears to fail in a large fraction of adult women, very few of these individuals have any difficulty standing upright, indicating that the postural reflex arc controlling soleus activity is intact. This observation sets the stage for a

We have pursued this hypothesis that the postural reflex arc regulating soleus activity is intact in women with inadequate fluid return from the lower limbs, and our experimental results support both the contention that this postural reflex is operational, and that exogenous activation of this soleus reflex arc is sufficient to significantly increase venous and lymphatic return from the lower limbs. Initial work focused on identifying the characteristics of the stimulus necessary to activate the soleus reflex and we observed that a micromechanical stimulation of plantar surface at 45 Hz, with a magnitude of 10 micrometers or greater was sufficient. This observation is consistent with the activated mechanoreceptors on the foot being the Meisner corpuscles [19]. A stimulus of this nature applied to the frontal plantar surface was found to completely block the drop in BP and increase in HR observed in women who could not maintain fluid return from the lower limbs during quiet sitting (Figure 7) [15]. Further studies on the mechanism underlying these clinical observations have shown that the plantar reflex stimulation has no effect on lymphatic microfiltration rate, but rather increases the isovolumetric lymphatic pressure, as well as significantly enhancing perfusion in the lower

As importantly, activation of the second heart (soleus) has been found to effectively in‐ hibit interstitial fluid pooling in adult women [17]. Following a 30 minute quiet sitting period during which a population of women (N=24) were observed to pool extensively (using air plethysmography), the subjects were exposed to 20 minutes of continuous plantar stimulation sufficient to activate the soleus muscle. Activation of the stimulus was found to result in an immediate drop in calf volume, which is interpreted to be due to the rapid decrease in venous volume (Figure 8) [17]. This rapid volume decrease was then followed by a sustained slower decrease in calf volume consistent with interstitial fluid migration to the initial lymphatics with subsequent ejection to the collecting lym‐ phatics and back to the heart. Sustained stimulation with continuous blood pressure monitoring confirms that the ejected fluid is returning to the heart per the associated in‐

**Figure 7.** Efficacy of soleus muscle activation, through its postural reflex arc, to prevent blood pressure drop in adult women. *From Madhavan, et al., 2005.* **Figure 8.** Efficacy of second heart stimulation, through the plantar reflex, to reverse interstitial fluid pooling in adult women. *From Goddard, et al., 2008.* 

**Figure 8.** Efficacy of second heart stimulation, through the plantar reflex, to reverse interstitial fluid pooling in adult women. *From Goddard, et al., 2008.*

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Y = 26.2 - 532 X

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R2 = 0.4 p = 0.18

Device Use (Hrs/day)

**Figure 10.** Change in lower limb body fluid over a one month time period as a function of average daily use of plantar

The recent research on second heart activity has largely relied on measurements such as continuous (beat-to-beat) blood pressure monitoring, air plethysmography, electrical impe‐ dance plethysmography, and strain-gage plethysmography. However, none of these techni‐ ques represent a practical technique for the clinical environment. We would suggest that the critical factors in diagnosing inadequate second heart activity are the creation of an extended time period of orthostatic stress coupled with blood pressure monitoring and HR determina‐ tion. These can be readily accomplished utilizing either upright standing or extended sitting, though as many older individuals have difficulty standing quietly for extended time periods, an extended sitting protocol is likely the most practical. A useful approach would be to obtain the BP and HR from a patient upon entering the examining room and first sitting down, then having them continue to sit for another 30 minutes or more with BP and HR obtained at the 15 and 30 minute time points. HR increases of more than 5 bpm, coupled to BP decreases of more than 10 mmHg, or more specifically, a diastolic BP dropping below 60 mmHg, should be considered a strong indication of inadequate fluid return to the heart, with long term

implications for heart health and the development of extrinsic cardiomyopathy.


**7. Differential diagnosis**

reflex stimulation of the second heart. *After Pierce & McLeod, 2009*.



Change in leg volume (ml)



0

**Figure 9.** Influence of sustained second heart stimulation via the plantar reflex on systolic blood pressure during ex‐ tended orthostatic stress associated with extended sitting. A) Time course of change in systolic blood pressure with transition from sitting to supine position. Time constant of 30 minutes suggests that close to three hours are necessary for interstitial fluid in the lower limbs to be recovered into the circulatory system following a transition to a supine position. B) Ability of second heart stimulation to accelerate fluid recovery from the lower limbs. Left panel: recovery rate associated with supine rest; Middle panel: Pooling associated with quiet sitting; Right panel: Influence of plantar reflex stimulation of the second heart. *From Madhavan, et al., 2009.*

The potential for second heart stimulation to assist individuals with diastolic heart failure, and at stage NYHA III has been tested in a pilot clinical study wherein individuals were provided with a plantar reflex stimulation device to use in their home for a four week period of time [22]. Three men and three women (average age 68 years) were recruited into the study with a group average LVEF of 49.8%. Lower limb water content was assessed using Dual Energy X-ray Absorptiometry (DXA). The average daily use of second heart stimulation ranged from 0.2 hours per day to 1.8 hours per day, and the change in retained lower limb water over the one month study period was associated with daily stimulation use (Figure 10). On average, a significant (p=0.03) decrease in lower limb water mass of 0.5Kg was observed, ranging from no decrease to over 1 liter.

**Figure 10.** Change in lower limb body fluid over a one month time period as a function of average daily use of plantar reflex stimulation of the second heart. *After Pierce & McLeod, 2009*.

### **7. Differential diagnosis**

**Figure 9.** Influence of sustained second heart stimulation via the plantar reflex on systolic blood pressure during ex‐ tended orthostatic stress associated with extended sitting. A) Time course of change in systolic blood pressure with transition from sitting to supine position. Time constant of 30 minutes suggests that close to three hours are necessary for interstitial fluid in the lower limbs to be recovered into the circulatory system following a transition to a supine position. B) Ability of second heart stimulation to accelerate fluid recovery from the lower limbs. Left panel: recovery rate associated with supine rest; Middle panel: Pooling associated with quiet sitting; Right panel: Influence of plantar

The potential for second heart stimulation to assist individuals with diastolic heart failure, and at stage NYHA III has been tested in a pilot clinical study wherein individuals were provided with a plantar reflex stimulation device to use in their home for a four week period of time [22]. Three men and three women (average age 68 years) were recruited into the study with a group average LVEF of 49.8%. Lower limb water content was assessed using Dual Energy X-ray Absorptiometry (DXA). The average daily use of second heart stimulation ranged from 0.2 hours per day to 1.8 hours per day, and the change in retained lower limb water over the one month study period was associated with daily stimulation use (Figure 10). On average, a significant (p=0.03) decrease in lower limb water mass of 0.5Kg was observed, ranging from

reflex stimulation of the second heart. *From Madhavan, et al., 2009.*

no decrease to over 1 liter.

276 Cardiomyopathies

The recent research on second heart activity has largely relied on measurements such as continuous (beat-to-beat) blood pressure monitoring, air plethysmography, electrical impe‐ dance plethysmography, and strain-gage plethysmography. However, none of these techni‐ ques represent a practical technique for the clinical environment. We would suggest that the critical factors in diagnosing inadequate second heart activity are the creation of an extended time period of orthostatic stress coupled with blood pressure monitoring and HR determina‐ tion. These can be readily accomplished utilizing either upright standing or extended sitting, though as many older individuals have difficulty standing quietly for extended time periods, an extended sitting protocol is likely the most practical. A useful approach would be to obtain the BP and HR from a patient upon entering the examining room and first sitting down, then having them continue to sit for another 30 minutes or more with BP and HR obtained at the 15 and 30 minute time points. HR increases of more than 5 bpm, coupled to BP decreases of more than 10 mmHg, or more specifically, a diastolic BP dropping below 60 mmHg, should be considered a strong indication of inadequate fluid return to the heart, with long term implications for heart health and the development of extrinsic cardiomyopathy.

### **8. Summary and conclusions**

Second heart failure, which occurs in close to 50% of women, represents a common etiology in extrinsic heart failure and cardiopathy. Clinical recognition of this condition opens the opportunity for early diagnosis and intervention, reducing the long term risk for this substan‐ tial subpopulation of women, with the potential to maintain a much higher quality of life into old age. Simple office tests of temporal changes in blood pressure and heart rate over 30 minutes of quiet sitting can reveal significant pooling associated with failed second heart activity. Augmenting venous return to the right heart to improve atrial refilling will allow for improved stroke volume and thus improved peripheral and cerebral blood flow. Early interventions can include specific exercises to train up the soleus muscle, lifestyle changes which challenge the postural reflexes; or utilization of extrinsic stimulation technology.

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