My love-hate relationship with my little black box

by Carolyn Thomas    @HeartSisters

Every morning, I clip it onto my belt, or tuck it into a hip pocket.  I very carefully attach its sticky little electrode pads onto the skin just over my heart, tucking their long black wires under my clothing. Lately, I also have to hold the electrodes in place on my skin with surgical tape because they’re starting to lose their stickiness after so much daily wear. I turn on the black box at my waist, and adjust its two knobs to the correct power levels. I feel a prickly little buzz pulsating across my chest.

It’s called Transcutaneous Electrical Nerve Stimulation (TENS), and it involves electrical impulses called neuromodulation to treat the chest pain (angina) of Inoperable Coronary Microvascular Disease (MVD) – a disorder of the smallest of the coronary arteries (too small to stent, too small to bypass).

My portable TENS unit is about the size of an average cell phone. You may know the much larger version of this machine if you’ve ever had physiotherapy treatments following a muscle injury.  The only wounded muscle it’s working on for me now, however, are those in my heart. Emerging cardiac research is showing that, just as the TENS machine works on improving blood flow, reducing inflammation and speeding up healing for an injured shoulder or knee, it may bring the same benefits to heart patients with MVD like mine.

But I do have a love-hate relationship with my little black box. 

I was told by my cardiologist that research suggests significant success using TENS neuromodulation to treat the debilitating chest pain of angina. Since 2001, the U.K. National Refractory Angina Centre has in fact recommended TENS therapy for persistent angina in heart patients:

“Neuromodulation owes its origins to Melzack and Wall’s gate theory of pain that predicted that stimulation of vibratory afferent nerves would reduce or gate the transmission of pain traffic relaying through the spinal cord at the same point.

“Transcutaneous electrical nerve stimulation (TENS) was specifically designed to make use of this predicted effect and was used to treat a variety of pain conditions before it was shown to be effective in angina.

“Neuromodulation should be offered as part of a multidisciplinary angina management programme based on the current guidelines.

My cardiologist prescribed a TENS unit to relieve refractory angina – mysteriously ongoing chest pain that does not respond to conventional drug therapy – since my heart attack. It cost about $120, a tax deductible medical expense here in Canada. His initial directions: turn it on twice a day, 30 minutes at a time.

New drugs and then more new drugs had not helped relieve these distressing and debilitating angina symptoms at all. Even a second admission to the hospital’s cardiac unit for another invasive procedure showed no new coronary artery blockages – a relief for those of us with stainless steel stents implanted inside our coronary arteries.

But those results also felt to me like ‘good news, bad news’. 

The good news: my symptoms were not due to stent failure. 

The bad news: my symptoms were not due to stent failure.

Had this ongoing chest pain been due to a good ol’ garden variety blockage within the stent or another major coronary artery, cardiologists may have been able to identify and address that.

But now what?

The new diagnosis emerged: Inoperable Coronary Microvascular Disease (MVD) involving the very smallest of the coronary arteries. It’s a painfully debilitating condition, usually missed using conventional cardiac diagnostic tools – and thus difficult to diagnose appropriately. UPDATE: Although previously considered to be more often seen in women, studies now suggest that both men and women are affected equally by MVD.

My revised diagnosis of MVD also prompted my cardiologist to refer me to the Regional Pain Clinic at our local hospital, and my first meeting with my new pain specialist, a charming pharmacist-turned-family doctor-turned anaesthesiologist, who is (just my luck!) an internationally-known expert on intractable pain management in heart patients.

In fact, he had spent a year doing a medical fellowship in Sweden studying this particular treatment for MVD. Just as in the U.K. and elsewhere, neuromodulation therapy in Sweden is widely recommended because it’s an effective, non-drug, non-invasive option to treat Inoperable Coronary Microvascular Disease and refractory angina.

These are diagnoses for which our conventional “revascularization” cardiac procedures like stents or bypass surgery provide no benefit.

My pain specialist prescribed a stepped-up one-month trial wearing my TENS unit every day, all day long instead of just for two 30-minute periods per day.

After a successful month of this revised routine (amazingly, with significantly reduced need for my nitro to address chest pain), he pronounced that I might also make an excellent candidate for an invasive surgical procedure called a Spinal Cord Stimulator Implant (SCSI). Neurostimulation like this is sometimes used in patients with angina when other therapies have failed.  It’s has been shown to increase coronary blood flow, to reduce the duration and frequency of anginal attacks, and to reverse ST-segment depression during stress testing.(1)

At the Pain Clinic, I listened to my pain specialist’s carefully detailed explanation of the SCSI procedure to manage chest pain.

But ultimately, I decided that any invasive surgical treatment beginning with the words “spinal cord” seemed too overwhelming for me to contemplate at this time, especially when my little portable TENS unit seems to be doing the trick for now.

Another effective therapy sometimes used to temporarily treat the pain of Inoperable Coronary Microvascular Disease is a nerve block procedure called a stellate ganglion block (SGB).

My pain specialist explained to me that this involves an injection of local anesthetic to block the sympathetic nerves located in the neck. An injection at these nerves may reduce pain symptoms of intractable angina for a period of up to four months.  SGB is also used to see if blood flow can be improved in those patients with circulation problems that are related to vascular disease. This procedure is already in widespread use in a variety of chronic pain conditions, and also has a history of use in the management of angina. (2)

Instead of either of these options for the time being, I’ll continue to have my progress with my little black box monitored at ongoing follow-up visits to the Pain Clinic.

My pain specialist assured me (and then produced copies of medical journal articles* to further explain) that the electrical current produced by both my little black box and by the Spinal Cord Stimulator Implant actually in itself produces some remarkable therapeutic effects on heart function.

Although he also told me that, unfortunately, “very few” of his Pain Clinic referrals are heart patients like me, we know that electricity to treat all types of pain has been used as far back as 63 A.D. Back then, it was reported by Scribonius Largus that leg muscle pain could be relieved by standing on an electrical eel at the seashore.

Electricity to treat cardiac pain works by modifying the neurologic input and output of the heart by delivering a very low-dose electrical current. This causes neural fibres to then release something called peptides into the coronary blood flow that actually reduce the heart muscle’s demand for oxygen. In addition, peptides can help to widen those small blood vessels of the heart (vasodilation) that in turn improves blood flow to the most diseased region of heart muscle.

So my little black box works not just by offering me 12+ hours of reasonable relief from debilitating daily chest pain, but it also seems to be actually helping open up those microvascular coronary arteries.

My need to take nitroglycerin these days for chest pain, for example, is significantly reduced – something that I had previously needed sometimes 3-4 times during a “bad day” to control debilitating – and terrifying – chest pain.  We had considered nitro patches or long-acting nitro pills, but because my angina pain was wildly episodic, the TENS unit looked like a win-win option.

But along with this development, I discovered in the very early days a new kind of debilitating experience until I learned how to manage it.  As I told my doctor:

Wearing this TENS unit is like having somebody standing on my foot all day long.”

It wasn’t particularly painful, but the distraction factor could drive you stark raving mad. I asked him how much of my newfound pain relief was due to the therapeutic effectiveness of the TENS electrical m, and how much just to the extreme distraction of the current buzzing across my chest every few seconds, hour after hour, all day long.

I found, for example, that until I got used to it, this distraction made it difficult to drive while the TENS was turned on.  My early morning walks had me stopping every 10 steps to clutch my chest, all the while assuring my alarmed walking buddies that I wasn’t having another heart attack, but I was merely trying to get used to the electrical fireworks going on inside my body.  Even conversations were difficult at first, as every few seconds I felt compelled to s-l-o-w down and focus on the fireworks instead of on what others were saying.

The good news, delivered during my last visit to the Pain Clinic, was that I’m now allowed to turn the dial down – way down! – to an almost imperceptible electrical buzz.

My pain specialist explained to me that recent research has shown similar cardiac benefits using extremely low levels of electrical simulation compared to my annoyingly distracting higher levels. He told me of one of his heart patient who had turned his TENS unit settings up so high that his pecs could be seen dancing and pulsating through his shirt – a flawed assumption that ‘if a little is good, then more is better’.

These days, I’m finally getting used to strapping on my little black box every morning as part of a normal routine.

This week, I’ve even replaced the annoyingly itchy surgical tape with several strips of a new hypo-allergenic paper tape which don’t cause nearly as much skin irritation. But they also don’t stick as well, unfortunately, particularly in hot weather, which has caused quite a few embarrassing public incidents this past summer involving my newly-freed electrodes flapping in the breeze around my knees.

As my pain specialist explains, the small but mighty TENS unit is actually helping my coronary arteries bear their workload in spite of Inoperable Coronary Microvascular Disease.

I certainly don’t want to return to those terrifying bouts of chest pain and subsequent nitroglycerin dependence – so I’ll continue my attempts to embrace this little miracle device riding on my hip.

Although I may give in occasionally to whining and wimping about wearing my little black box, I’m also gobsmacked that more heart patients are not being offered this treatment option.

Why aren’t more patients offered this non-drug, non-invasive, inexpensive and effective therapy for the debilitating symptoms of chronic angina?

When I recently asked another MVD patient suffering with refractory angina if she had asked her own cardiologist about using this particular pain management option, her shocking response to me was:

“I had mentioned this to my cardiologist and he wanted nothing to do with it ( ‘…not his field’).”

“Not his field”?  If addressing crushingly debilitating angina pain in his heart patients is “not his field”, what on earth is?

♥  ♥  ♥


TENS UPDATE, November 29, 2011:   At today’s regular follow-up appointment at the Pain Clinic, my pain specialist added two simple recommendations for all heart patients wearing portable TENS units:

1.  Replace the sticky pads on your TENS every 6-8 weeks if you, like me, are wearing your TENS from morning to night, seven days a week. In between replacement, follow the device instructions for regularly cleaning the sticky pads (I use a soft baby toothbrush for this).

2.  Change the internal setting on your TENS from ‘modulate’ to ‘constant’ and vice versa (some reports suggest that this little adjustment can  mean improved pain management results).

.NOTE FROM CAROLYN:   I wrote more on making life easier for heart patients in my book, A Woman’s Guide to Living With Heart Disease(Johns Hopkins University Press), you can ask for it at your local bookshop, or order it online (paperback, hardcover or e-book) at Amazon, or order it directly from my publisher, Johns Hopkins University Press (use their code HTWN to save 30% off the list price).

See also:

You can watch videos of the 2019 INOCA International “Meeting of the Minds” microvascular disease conference keynote speakers in London, including Dr. Juan-Carlos Kaski’s presentation.

UPDATE November 2019: Diagnostic tools used to identify coronary microvascular dysfunction

EECP Therapy – and Wearing Fun Socks

No Blockages: Living with Non-Obstructive Heart Disease

How Women Can Have Heart Attacks Without Having Any Blocked Arteries

“His and Hers Heart Attacks”

Misdiagnosed: Women’s Coronary Microvascular and Spasm Pain

Coronary Microvascular Disease: a “Trash Basket Diagnosis”?

The Freakish Nature of Cardiac Pain

Brain Freeze, Heart Disease and Pain Self-Management

Chest pain While Running Uphill

(1)  Mehta PK, Bairey Merz CN. Treatment of stable angina in subjects with evidence of myocardial ischemia and no obstructive coronary artery disease. In: Bonow RO, Mann DL, Zipe DP, Libby P, editors. Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Philadelphia: Saunders/Elsevier; 2008.
(2) “Influence of Stellate Ganglion Blockade on Angina Pectoris and the Post Exercise Electrocardiogram”, Moore DC. Stellate ganglion block. Springfield, IL: CC Thomas, 1954; Wiener L, Cox JW. American Journal of Medical Science, 1966;252:289-295

The medical journal articles shared by our Regional Pain Clinic are:

1.  “Spinal Cord Stimulation Improves Functional Status and Relieves Symptoms in Patients With Refractory Angina Pectoris: the First Placebo-Controlled Study”, Drs. S. Eddicks, K. Maier-Hauff, M. Schenk et al, Heart 2007 03:585-590
2.  “Treatment of Inoperable Coronary Disease and Refractory Angina”, Dr. N.Svorkdal, Seminars In Cardiothoracic and Vascular Anesthesia, Vol 8, No 1 (March) 2004
3.  “Spinal Cord Stimulation in the Treatment of Refractory Angina”, Drs. R. Taylor, J. De Vries, E. Buchser, M.DeJongste,BMC Cardiovascular Disorders, March 25, 2009, 9:13
4.  “Spinal Cord Stimulation Improves Ventricular Function and Reduces Ventricular Arrhythmias in a Canine Post-Infarction Heart Failure Model”, Circulation, American Heart Association, 2009, 120:286-294.
5.  “Trans-Cutaneous Electrical Nerve Stimulation in Unstable Angina Pectoris”. Drs. Borjesson M, Eriksson P, Dellborg M, et al: Coron Artery Dis 8:543-550, 1997.
6. “Temporary sympathectomy in the treatment of chronic refractory angina”. R Moore et al. J Pain Symptom Manage. 2005 Aug;30(2):183-91.

35 thoughts on “My love-hate relationship with my little black box

  1. Hello, as far for using a TENS unit, what are your settings at for it? I have a unit and am trying to figure out electrodes placement, to use 2 or 4 pads and what frequency and duration and other settings to make this work for me.

    Liked by 1 person

    1. Hello Mike – the answers to your questions might vary from person to person, so I’ll just share what my own cardologist and pain specialist have recommended (not meant as specific medical advice).

      As I mentioned in this article, I learned that TENS unit settings do not have to be at maximum power to obtain a benefit. I turn on my power knob just until I can feel the first ‘buzz’ across my chest, and then I turn it slightly back down until it’s barely perceptible. I generally use 2 pads in the front (one sort of central sternum and the other slightly to the left of the first) when I’m out and about, but if I’m at home and can lie down, I like to add two more on my back directly opposite their counterparts on the front of the body. Lying down helps to anchor the back pads in place. On a bad day for refractory angina, I may wear my TENS unit all day long beneath my clothes. On a (very) good day, I may not use my TENS unit at all. In the daytime, I use paper-based surgical tape (NOT the thicker adhesive ones which I found can cause awful skin irritations) to keep each electrode pad in place. I don’t use my TENS unit at night as my symptoms don’t seem to flare overnight. Play around with your settings and duration to figure out what will work best for you…


  2. Thank you for this information.
    Newly diagnosed for MVD and am gathering as much info as possible before I see my cardiologist next week.
    QUESTION to all :
    Is anyone familiar with “chelation therapy” for helping to remove plaque from arteries??
    Thank you so much.
    Scottsdale Az

    Liked by 1 person

    1. Sherry, chelation therapy is an interesting subject. This therapy involves a chemical process used to removed toxic metals or minerals from the body. It’s been scientifically proven as an effective treatment of mercury or lead poisoning for many years. Another longtime theory has claimed that this treatment can somehow bind the calcium that’s in the coronary artery plaque of heart patients; the calcium will then be flushed away in urine. A study called TACT (Trial to Assess Chelation Therapy) was published in 2013 in the Journal of the American Medical Association. Until TACT, despite rave reviews from alternative medicine followers, there was very little if any good quality research on this therapy, which meant that most traditional physicians were not interested in it.

      The TACT study was conducted at 134 research sites in the United States and Canada on a total of 1,708 patients aged 50 years or older (but only 18% of them women), all of whom had had a myocardial infarction (heart attack) prior to starting the study. These patients were then followed for 55 months. The results were mixed: no significant advantage for most heart patients were reported, except for one specific group studied: the older high-risk patient living with both diabetes and heart disease. These patients made up about 1/3 of the TACT participants; they showed a 41% overall reduction in the risk of any cardiovascular event; a 52% reduction in recurrent heart attacks; and a 43% reduction in death from any cause compared to the younger non-diabetes patients.

      Still, neither the American Heart Association nor the American College of Cardiology recommend chelation therapy for heart patients, and the Food and Drug Administration (FDA) has NOT yet approved chelation therapy for use as a heart disease treatment. If you’re an older heart attack survivor also living with diabetes and are interested in this treatment option, discuss this with your physician. Do NOT waste your money or risk your health by purchasing over-the-counter products claiming “do-it-yourself” chelation. Here’s more about the TACT study.


  3. Can you tell me names of sites near eastern Pennsylvania to have CMVD accurately diagnosed. I know there were 4 sites in the WISE trial led by Noel Bairey Merz.


    1. Hi Jerri – I’m not familiar with Pennsylvania, but I know that Allegheny General Hospital – Hahnemann School of Medicine in Pittsburgh and the University of Pittsburgh were study sites.


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  5. I have a home TENS unit. I have SVT. I place the pads on my chest. I can feel my chest discomfort go away. It is very true what you just said – it does help. I just did it to try it out. And I’m on meds.

    Liked by 1 person

  6. Where do you place the pads for MVD? I was just diagnosed with this. I already have a prescription TENS unit for my lower back. The heart medication makes me MISERABLE! My normal bp is 90/60 before medication.


    1. Hi Tina – placement of the four pads depends on what I’m doing. If I’m lying down (it’s how I started this therapy, twice a day, 30 min/time) I attached two on my chest (one central and one immediately beside it slightly to the left) and two directly opposite on my upper back. If I’m walking around, I sometimes use two on the chest only. But if symptoms are really bad, I revert back to using four, two front and two in the back.


  7. Hi Carolyn it is completely maddening that more cardiologists are not more aware of this. I have suffered with MVD for almost two years and all my doctors could recommend were more or different drugs (like nitro patches to control chest pain symptoms). Oddly the only remedy that has even hinted at relief so far has been swimming – the exercise I believe is strengthening my heart muscle, but I came to this conclusion on my own, no doctor ever recommended I exercise more. I’m going to forward this article plus links to them! THANKYOU!!!!

    Liked by 1 person

  8. Like you, Carolyn, I too have been diagnosed with inoperable coronary microvascular disease after 18 months of truly awful cardiac symptoms and many wrong turns and dead ends. Now I’m finally seeing a new cardiologist who actually has experience with MVD patients, knows his research and is open to all therapies. He actually “gets” it. I’m going to print this article and ask him about this TENS therapy at next week’s appointment. THANK YOU so much for this. I’m so hopeful.

    Liked by 1 person

  9. After two years of being told my chest pain was “all in my head” I was finally diagnosed with MVD. My new meds help now, but still many bad episodes of symptoms. Why hasn’t my cardiologist recommended a TENS unit like yours?

    Liked by 1 person

  10. Microvascular disease is only recently becoming understood by doctors. Thx for telling us about this non-drug non-invasive option for MVD patients. Good luck to you, keep up the good work here.

    Liked by 1 person

  11. Thanks for this info – I have printed it off and will show this to my cardiologist. We’ve just been upping my meds one after another trying to get this “inoperable coronary microvascular disease” in check but with only moderate success. This may be finally a treatment that helps. He has never mentioned a TENS unit to me.

    Liked by 1 person

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  14. Carolyn,

    I also had TENS treatment for back issues, simultaneously to the time when the mystery of my CP (Endo Dysfunction) was happening. At the time, I was trying to sort out the chest pain from the back pain – as the ischemia manifested as back tightness. I used to LOVE the TENS treatments and looked forward to feeling so good on those days. Now I understand why it was helping me. Thanks for the up close and personal account.


    Liked by 1 person

  15. Way to go, Carolyn!

    I wore one in the 90’s for back pain and it got me thru nursing school when an old back injury flared up. It was a wonderful resource and I wish more people knew about them. Glad to hear they are in the heart pain and heart healing management cadre.


    Liked by 1 person

      1. Hello Sonia – I can’t really say, as I am familiar only with the TENS unit that I have been using, recommended by my cardiologist. It’s called ProActive, from a Montreal company called AMG Medical. I had to have a doctor’s prescription to purchase it at a medical supply company. Click on the Where To Buy tab to find retailers near you.


        1. Hi Carolyn, I talked with my GP yesterday, but as expected she had no knowledge of TENS helping this condition but she did say it won’t hurt to; I am assuming the same reaction from my Cardiologist as well in a sense, but I did book an appt with a physio clinic here in Prince George next week and I’ll go frm there, wish me luck!

          Calcium Channel Blockers (CCB’s) are not a good idea for me my blood pressure is already LOW with the nitro combos!

          Liked by 1 person

          1. Hello Karen – right now, my Frequency setting is at 115 Hz (in a range from 2-150) and the Pulse width is 180 (range from 60-250). I play around with my settings frequently on a bad day, as suggested by my Pain Specialist; apparently even very low settings (barely perceptible ‘buzz’) are considered equally effective).


            1. Thank you so much for your reply. I had a heart attack 2 yrs ago & since then had so many problems, finally diagnosed with MVD & coronary artery spasm. Read your blog & my husband bought me a TENS machine. So here goes, willing to try anything for pain relief.

              Liked by 1 person

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